Add goreleaser with Homebrew tap and Docker publishing

[klaidliadon]

Summary

• Add goreleaser v2 config for cross-platform binary releases (darwin/linux/windows × amd64/arm64)
• Add release workflow triggered on v* tags (goreleaser + Docker image to ghcr.io)
• Add --version / -v flag to the ridl-lsp binary, with build-time version injection via ldflags
• Add Homebrew formula publishing to webrpc/homebrew-tap
• Add Dockerfile for ghcr.io/webrpc/ridl-lsp container image

Prerequisites

• HOMEBREW_TAP_GITHUB_TOKEN secret must be available to this repo (check if org-level or needs to be added per-repo)

Test plan

• make build && ./bin/ridl-lsp --version prints version
• Tag a v0.x.0 release and verify goreleaser workflow runs
• Verify Homebrew formula is pushed to webrpc/homebrew-tap
• Verify Docker image is published to ghcr.io/webrpc/ridl-lsp