Cooper Gillan

https://github.com/braintree/runbook/pull/54 originally attempted to add support for Ruby 3.1, but [the build failed](https://github.com/braintree/runbook/runs/4986638006?check_suite_focus=true) with some test failures. This should be investigated separately and the builds should be run for Ruby...

## Description Update the text of two links to match the actual link.

# Description Update some wording. Check the builds. @hectron

Add support for running `rustfmt` on each save

2

# What Add a one-line `rust_mappings.vim` file allowing `rustfmt` to be automatically run when a buffer is saved, then include that runtime in `vimrc`. Note that this only leveraging existing...

# What Add [`vim-crystal` plugin](https://github.com/vim-crystal/vim-crystal) # Why To add support for Crystal language files. # Checklist - [ ] Send RFC email to Braintree developers _if change may be impactful_....