add a README to the main directory

Author: nikomatsakis

README.md

@@ -1,5 +1,41 @@
-# wg-traits
-
 Home of the "traits working group", affiliated with the compiler and
 lang teams. This repository is used to house draft RFCs, notes, and
 other related documents.
+
+# Scope and purpose
+
+The **traits** working group is dedicated to improving the trait
+system implementation in rustc. This working group is a collaboration
+between the [lang team] and the compiler team. We have a number of inter-related
+goals:
+
+- designing new trait-related language features;
+- documenting and specifying the semantics of traits in Rust today; and,
+- improving the trait solver implementation in rustc.
+
+[lang team]: https://github.com/rust-lang/lang-team/
+
+A big part of this work is transitioning the compiler to use a
+[Chalk-style] solver, but along the way we hope to make targeted fixes
+to the existing solver where needed.
+
+[Chalk-style]: https://github.com/rust-lang-nursery/chalk
+
+# How to participate
+
+## Chat forum
+
+On [the rust-lang Zulip][z], in [the `#t-compiler/wg-traits` stream][s].
+
+[z]: https://rust-lang.zulipchat.com/
+[s]: https://rust-lang.zulipchat.com/#narrow/stream/144729-t-compiler.2Fwg-traits
+
+## Weekly triage meeting
+
+There is a weekly triage meeting which you will find on the [compiler
+meeting calendar][c]. The purpose of this meeting is to take stock of
+where we are and figure out what to do next. The meeting takes place
+on [Zulip][z] in a dedicated topic of the [the `#t-compiler/wg-traits`
+stream][s].
+
+[c]: https://github.com/rust-lang/compiler-team#meeting-calendar