Add known_issues.md for tracking core language issues

Author: aclysma

known_issues.md

@@ -0,0 +1,31 @@
+# Known Issues
+
+One of the goals of this working group is to improve the user experience of people using rust for game development.
+
+**This document tracks issues that we as a group would like to raise for the core Rust language team.** This may
+include missing functionality, or problems that impede productivity. This is not an exhaustive list, and only 
+includes language-level issues. 
+
+If you feel that something should be added to this list:
+ * Please open an issue on this or another repository so that we can link to it
+ * Submit a PR to this document
+
+If you're not sure, just open an issue in this repo. We're happy to help!
+
+## IDE/Debugging Experience
+* https://github.com/rust-gamedev/wg/issues/20 - Map/Set in .natvis files
+* https://github.com/rust-gamedev/wg/issues/22 - RLS for huge projects
+* https://github.com/EmbarkStudios/rust-ecosystem/issues/8 - RLS in VS Code robustness & performance
+* https://github.com/EmbarkStudios/rust-ecosystem/issues/9 - Better debugger experience in VS Code
+ 
+## Debug Performance
+* https://github.com/rust-gamedev/wg/issues/32 - Selective Enabling/Disabling optimizations at a crate/file/function level
+    * Profile overrides do not work for code using generics (such as nphysics) https://github.com/rust-lang/rust/issues/63484
+* https://github.com/EmbarkStudios/rust-ecosystem/issues/5 - More efficient runtime code generation for debug builds
+ 
+## Iteration Times
+* https://github.com/EmbarkStudios/rust-ecosystem/issues/13 - Dynamic libraries (dll/dylib) for fast iteration
+* https://github.com/EmbarkStudios/rust-ecosystem/issues/11 - Distributed compilation for fast iteration
+ 
+## Runtime Performance
+* https://github.com/EmbarkStudios/rust-ecosystem/issues/2 - fast math support