Explore macro autocomplete with Rust Analyzer

[greyblake]

See resources:

• https://www.reddit.com/r/rust/comments/1f81d2v/comment/llcayj8/
• https://elastio.github.io/bon/blog/bon-builder-generator-v2-release#experimental-completions-with-rust-analyzer
• https://blog.emi0x7d1.dev/improving-autocompletion-in-your-rust-macros/