Implement code action to replace ==/!= with ===/!==

[fredrikekre]

This implements a new code action, CompareNothingWithTripleEqual, which
offers to replace == and != with === and !==, respectively, for the
corresponding linter warning(s).

[fredrikekre]

From https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_codeAction it looks like the response can also contain the diagnostics that the edit resolves? I am not sure how to pass that, and if it is necessary (the file will be relinted anyway, is it just so users can see that it actually resolves something?

[fredrikekre]

I guess those would show up as quickfixes to the linter messages or something?

[fredrikekre]

I played around a bit more but I think that linking diagnostics to fixes like that require quite some more changes (e.g. returning CodeActions instead of Commands from codeAction request, and support for data in various structs, which is in version 3.16) so I think that can be done in a future PR.