Test string util classes

[rubysdeadname]

Hey team,

I noticed that the coverage for this project is quite low, so I've written a few tests to boost it a little bit. Hopefully this helps a little, but if it complicates things then feel free to close this issue and my PR.

I have written tests for string-util.ts in the aura server and strings.ts in lightning lsp common.

Thanks!

[lcampos]

Closing this since the changes were merged. Thanks again for the contribution @gabrielbarker