Mark extension as deprecated

[Splines]

Thanks a lot for your extension, it has served us well at MaMpf during the last two years ❤

Now that the extension is deprecated, it'd be nice to also make this apparent in the VSCode Marketplace. I think the only way to do this right now is to post a comment on this thread.

[connorshea]

I'm glad to hear it was useful to you all for the last few years! Thank you :) Hopefully the Ruby LSP extensions fits your needs here, as it does mine nowadays.

I've requested the deprecation in that thread now. I had been meaning to do that, but got busy with some other obligations in the last few weeks, and had also been waiting to get permission from the ruby-lsp-rspec folks to recommend their gem as part of the deprecation message (which I did get permission for ~two weeks ago).