feat(tools) Add `document_save` tool

[Gh61]

Hello,
thank you for this extension. It is very useful for integrating AI with Visual Studio.
There are a few things missing that would make it work better for our use case.
If you do not mind, I would like to suggest a few improvements. I may even implement some of them myself in the future if I find the time.

Updates performed by the MCP server are not committed to the file.
So when the AI edits a file through the MCP server, the file is not saved and therefore cannot be used for debugging or building.
Currently, the only way to save a file is by calling document_close with save=true, which is not ideal.

Please add a document_save tool.

[CalvinAllen]

@Gh61 Will be in the next release! (today, probably)

[Gh61]

Thank you!