Add debugging

[peter-bread]

This will likely be a fairly large feature.

Needs to use nvim-dap and overseer.nvim.

See also https://youtu.be/47UGK4NgvC8.

• Initial DAP plugin setup (+ dependencies)
• Implement utility function in peter.util.plugins.languages called dap or debug to extend opts.
• Integrate with overseer.nvim to use .vscode/tasks.json for pre and post debug tasks (see feat(plugins): add overseer.nvim #38 for preliminary work (barely any tbh))

Also see 6f77d9a.