Adds support for additional language IDs - terraform and terraform-vars

[Gogotchuri]

This issue arose while I was working on the USAGE.md ( #48 ) rewrite and testing tofu-ls with several different editors.
To facilitate integration with a wide range of editors and IDEs, we add support for the language IDs: 'terraform' and 'terraform-vars'.
Remapping extensions and language names can be a bit cumbersome in some cases, and this change will eliminate the need for it.
In earlier iterations, we modified the language IDs to opentofu and opentofu-vars. Now we extend the language server to accept the other pair too.

Checklist

• I have read the contribution guide.
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Go checklist

• I have run golangci-lint on my change and receive no errors relevant to my code.
• I have run existing tests to ensure my code doesn't break anything.
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[diofeher]

Interesting @Gogotchuri ! Are you testing with both extensions installed at the same time?

[Gogotchuri]

Interesting @Gogotchuri ! Are you testing with both extensions installed at the same time?

I haven't done testing in VSCode, but if you could, that would be nice. I'm not sure this will solve the issue you are hinting at, but it avoids a lot of unnecessary complications in editor usage.

[diofeher]

Great idea @Gogotchuri ! Thanks for implementing it :)