Establish a pattern for welcome bots to help people with committed

[epage]

As suggested in https://github.com/crate-ci/typos/pull/387

Options I found

• https://github.com/marketplace/actions/welcome-new-contributors
• https://github.com/marketplace/actions/welcome-new-users
• https://github.com/rust-lang/highfive

High Five is the nicest with path-based messages,expected branch handling, etc. The problem is its a bit more involved to setup.