LSP setup

[oscarlevin]

This will build off of the work of @siefkenj from #22, which has been integrated into the updated main. Draft for now while I learn how this LSP thing works.

[angelozerr]

I wonder why you need an LSP support for pretext.

Do you want to skip vscode-xml? Which features will provide the lsp server?

[oscarlevin]

I have already implemented a few language features that really should be part of an LSP rather than the "old way" directly in the extension: formatting, context aware completions, xref suggestions. All of these are particular to how PreTeXt works and there don't seem to be options to customize the vscode-xml lsp to make them work.

Additionally, some users have been having trouble getting the vscode-xml extension to validate consistently; likely an issue with using the binary or not, but I haven't been able to figure out what the cause is. My hope is that since we don't need all the features of the vscode-xml lsp we can implement the lsp for our features just in node.

Also, I like learning new things :)

[angelozerr]

I have already implemented a few language features that really should be part of an LSP rather than the "old way" directly in the extension: formatting, context aware completions, xref suggestions. All of these are particular to how PreTeXt works and there don't seem to be options to customize the vscode-xml lsp to make them work.

Additionally, some users have been having trouble getting the vscode-xml extension to validate consistently; likely an issue with using the binary or not, but I haven't been able to figure out what the cause is. My hope is that since we don't need all the features of the vscode-xml lsp we can implement the lsp for our features just in node.

Also, I like learning new things :)

I see, thanks for your feedback and enjoy with your lsp stuff, it so interesting!

[oscarlevin]

This PR, in addition to getting the general LSP set up, implements completions through it, using imported rng schemas to handle the completions. Merging now even though there are additional features to port to the LSP.