Add Intial DocC docs

[0xTim]

Adds some additional documentation. I don't know how far you want me to go with documenting everything so let me know. This should at least get the current APIs rendered on SPI. As an aside I'm not a huge fan of linking out to the CryptoKit docs since not everything is available here, all the code is already documented here and most of the tutorials and articles on developer.apple.com for CryptoKit refer to Apple Platform specific stuff, like interacting with the keychain, that is not applicable here.

Resolves #273

Checklist

• I've run tests to see all new and existing tests pass
• I've followed the code style of the rest of the project
• I've read the Contribution Guidelines
• I've updated the documentation if necessary

If you've made changes to gyb files

• I've run .script/generate_boilerplate_files_with_gyb and included updated generated files in a commit of this pull request

Motivation:

Currently Swift Crypto has no documentation which is not great

Modifications:

Adds additional DocC scaffolding to take advantage of the DocC comments in Crypto and CryptoExtras. Adds an SPI config file for Swift Package Index

Result:

We will have some documentation

[0xTim]

@Lukasa can we get this looked at? Currently the SPI docs are just empty https://swiftpackageindex.com/apple/swift-crypto/3.10.0/documentation/crypto

[Lukasa]

Great, let's do it.

[fpseverino]

There are a couple of issues:

• for Crypto the docs are still empty, except for the new index.md landing page, I don't know why
• for _CryptoExtras the landing page is missing, I think because index.md starts with ``CryptoExtras`` and not ``_CryptoExtras`` (Rename _CryptoExtras to CryptoExtras #281 might fix this)

BTW I tested it locally with swift-docc-plugin, it's not published on SPI yet

[0xTim]

Are you building on Linux or macOS?

[fpseverino]

macOS 15.1.1

[fpseverino]

Ok the issue was the the development flag in Package.swift was set to false

[0xTim]

Ok I suspect that's the actual issue. Same with SPI. Docs build on macOS with a default manifest will use the code for macOS, which is nothing since it just re-exports CryptoKit. I'll get a fix up for both

[0xTim]

See https://github.com/apple/swift-crypto/pull/311/files