Add link to RLS/VSCode announcement

Is this the right way to submit a link? Looks like the above links are from last week, but I didn't delete them in this PR.

Author: nrc

drafts/2017-08-22-this-week-in-rust.md

@@ -37,6 +37,7 @@ If you find any errors in this week's issue, [please submit a PR](https://github
 * [This week in Rust docs 68](https://guillaumegomez.github.io/this-week-in-rust-docs/blog/this-week-in-rust-docs-68).
 * [These weeks in dev-tools 1](https://www.ncameron.org/blog/these-weeks-in-dev-tools-issue-1/).
 * [This week in Redox 28](https://redox-os.org/news/this-week-in-redox-28/).
+* [Annoucnement - try out Rust IDE support in Visual Studio Code](https://users.rust-lang.org/t/try-out-rust-ide-support-in-visual-studio-code/12407)
 
 # Crate of the Week