[AsyncStreaming] Exclude the proposal file from the target

[kSibalic]

Motivation

The generalized async streaming proposal, NNNN-async-streaming.md, lives in Sources/AsyncStreaming/ alongside the implementation. Because it is a Markdown document rather than a build input, SwiftPM reports it as an unhandled file on every build (#433):

warning: 'swift-async-algorithms': found 1 file(s) which are unhandled; explicitly declare them as resources or exclude from the target
    Sources/AsyncStreaming/NNNN-async-streaming.md

Modifications

The proposal is intentionally kept next to the implementation, so it is excluded from the AsyncStreaming target in Package.swift rather than being moved:

exclude: ["NNNN-async-streaming.md"]

Result

swift build no longer emits the unhandled-file warning, and the proposal stays alongside the implementation.

Resolves #433.

[FranzBusch]

This was intentionally not placed in that directory. Instead we can exclude this proposal file in our Package.swift.

[kSibalic]

This was intentionally not placed in that directory. Instead we can exclude this proposal file in our Package.swift.

Thank you Franz, makes sense. I have updated the PR to keep the proposal in place and exclude it via Package.swift instead.