make auto completion of single quotation possible

[harusaku]

Because I felt inconvenient not to close a single quotation automatically, I added the rule to language-configuration.json.

If there are some reasons why a single quote is not included in autoClosingPairs, please tell me about that.

[lnicola]

Hi! This extension has been less actively maintained lately and some users found they prefer https://github.com/rust-analyzer/rust-analyzer/ more. If you haven't already, you could give it a try.

rust-analyzer doesn't seem to include single quotes, so you could file the same PR over there. But I'm not convinced it's a good idea because of the Rust syntax for lifetimes, e.g.: fn foo<'a>(x: &'a i32). I imagine that adding quote pairs could get quite annoying in some cases.

[harusaku]

Thanks for your comments!
I am a beginner of Rust, and I don't know about the usage of a single quotation at Rust.
Also, I wasn't aware of the non-activeness of this extension. I'll check the other extension.
Thank you!!!