x/tools/gopls: auto-generate API diff for releases

[findleyr]

From our team meeting: gopls auto-generates documentation for both its workspace/executeCommand API and its settings.

We should use this metadata to generate an API diff to attach to our releases, similar to how cmd/api works in the Go repo.

This may have helped in golang/vscode-go#1549

CC @hyangah @stamblerre

[findleyr]

This is probably as simple as capturing internal/lsp/source/api_json.go for each release. We can check it in, similar Go's api/ directory.

This could also be used to generate 'added in gopls v0.7.0' commentary in our documentation.

[danishprakash]

I'd like to try this out @findleyr, let me know if that's okay.

[findleyr]

@danishprakash I believe @stamblerre already has an in-progress CL doing this.

[gopherbot]

Change https://golang.org/cl/327276 mentions this issue: gopls/api-diff: create api-diff command for gopls api