Add ruby-lsp to development gems

What does this MR do and why?

Adds ruby-lsp to development gems. This was also recently added to the gitlab-org/gitlab project: gitlab!136289 (merged). See https://github.com/Shopify/vscode-ruby-lsp#features for a list of the features.

This allows for some really nice tools in VS Code and other editors including rubymine-like debugging. This is similar to what pry can offer, but with a full UI built into the editor and really nice navigation during debugging:

Description	Screenshot
Showing the test UI interface
Ability to trigger test in the test interface, terminal, or Debug testing!
At a breakpoint during a debug test run
Ability to step through code and check variables at breakpoints

Author Check-list

• Has documentation been updated?