Add DocC catalog and README (#3)

Motivation:

We should have a README to explain what the package is and should point
to docs we publish to the Swift Package Index.

Modifications:

- Add a README
- Add a .spi.yml
- Add a DocC catalog

Result:

More docs

.spi.yml

@@ -0,0 +1,5 @@
+version: 1
+builder:
+  configs:
+    - documentation_targets: [GRPCProtobuf]
+      swift_version: 6.0

CONTRIBUTING.md

@@ -1,19 +1,4 @@
-# How to contribute
+# Contributing
 
-We definitely welcome patches and contributions to grpc-swift! Please read the gRPC
-organization's [governance rules](https://github.com/grpc/grpc-community/blob/main/governance.md)
-and [contribution guidelines](https://github.com/grpc/grpc-community/blob/main/CONTRIBUTING.md) before proceeding.
-
-Here are some guidelines and information about how to participate.
-
-## Getting started
-
-### Legal requirements
-
-In order to protect both you and ourselves, you will need to sign the
-[Contributor License Agreement](https://identity.linuxfoundation.org/projects/cncf).
-
-### Technical requirements
-
-Please see the [main gRPC repository](https://github.com/grpc/grpc) for
-more information about gRPC.
+Please refer to the contributing guide in the
+[`grpc/grpc-swift`](https://github.com/grpc/grpc-swift) repository.

README.md

@@ -0,0 +1,18 @@
+# gRPC Swift Protobuf
+
+This repository contains integrations with [SwiftProtobuf][gh-swift-protobuf]
+for [gRPC Swift][gh-grpc-swift-protobuf].
+
+- 📚 **Documentation** is available on the [Swift Package Index][spi-grpc-swift-protobuf]
+- 🎓 **Tutorials** are available in the documentation for `grpc/grpc-swift` on
+  the [Swift Package Index][spi-grpc-swift].
+- 💻 **Examples** are available in the `Examples` directory of the
+  [`grpc/grpc-swift`](https://github.com/grpc/grpc-swift) repository
+- 🚀 **Contributions** are welcome, please see [CONTRIBUTING.md](CONTRIBUTING.md)
+- 🪪 **License** is Apache 2.0, repeated in [LICENSE](License)
+- 🔒 **Security** issues should be reported via the process in [SECURITY.md](SECURITY.md)
+
+[gh-swift-protobuf]: https://github.com/apple/swift-protobuf
+[gh-grpc-swift-protobuf]: https://github.com/grpc/grpc-swift-protobuf
+[spi-grpc-swift]: https://swiftpackageindex.com/grpc/grpc-swift/documentation
+[spi-grpc-swift-protobuf]: https://swiftpackageindex.com/grpc/grpc-swift-protobuf/documentation

SECURITY.md

@@ -1,46 +1,4 @@
 # Security
 
-This document specifies the security process for gRPC Swift.
-
-## Disclosures
-
-### Private Disclosure Process
-
-The gRPC Swift team asks that known and suspected vulnerabilities be
-privately and responsibly disclosed by emailing
-[grpc-swift-security@group.apple.com](mailto:grpc-swift-security@group.apple.com)
-with the [details usually included with bug reports][issue-template].
-**Do not file a public issue.**
-
-#### When to report a vulnerability
-
-* You think you have discovered a potential security vulnerability in gRPC
-  Swift.
-* You are unsure how a vulnerability affects gRPC Swift.
-
-#### What happens next?
-
-* A member of the team will acknowledge receipt of the report within 3
-  working days (United Kingdom). This may include a request for additional
-  information about reproducing the vulnerability.
-* We will privately inform the Swift Server Work Group ([SSWG][sswg]) of the
-  vulnerability within 10 days of the report as per their [security
-  guidelines][sswg-security].
-* Once we have identified a fix we may ask you to validate it. We aim to do this
-  within 30 days. In some cases this may not be possible, for example when the
-  vulnerability exists at the protocol level and the industry must coordinate on
-  the disclosure process.
-* If a CVE number is required, one will be requested from [MITRE][mitre]
-  providing you with full credit for the discovery.
-* We will decide on a planned release date and let you know when it is.
-* Prior to release, we will inform major dependents that a security-related
-  patch is impending.
-* Once the fix has been released we will publish a security advisory on GitHub
-  and the [SSWG][sswg] will announce the vulnerability on the [Swift
-  forums][swift-forums-sec].
-
-[issue-template]: https://github.com/grpc/grpc-swift/blob/main/.github/ISSUE_TEMPLATE/BUG_REPORT.md
-[sswg]: https://github.com/swift-server/sswg
-[sswg-security]: https://github.com/swift-server/sswg/blob/main/process/incubation.md#security-best-practices
-[swift-forums-sec]: https://forums.swift.org/c/server/security-updates/
-[mitre]: https://cveform.mitre.org/
+Please refer to [SECURITY.md] in the
+[`grpc/grpc-swift`](https://github.com/grpc/grpc-swift) repository.

Sources/GRPCProtobuf/Documentation.docc/Documentation.md

@@ -0,0 +1,20 @@
+# ``GRPCProtobuf``
+
+A package integrating Swift Protobuf with gRPC Swift.
+
+## Overview
+
+This package provides two products:
+- ``GRPCProtobuf``, a module providing runtime serialization and deserialization components for
+  [SwiftProtobuf](https://github.com/apple/swift-protobuf).
+- `protoc-gen-grpc-swift`, an executable which is a plugin for `protoc`, the Protocol Buffers
+  compiler. An article describing how to generate gRPC Swift stubs using it is available with the
+  `grpc-swift` documentation on the [Swift Package
+  Index](https://swiftpackageindex.com/grpc/grpc-swift/documentation).
+
+## Topics
+
+### Serialization
+
+- ``ProtobufSerializer``
+- ``ProtobufDeserializer``