Add review guidelines

Extends committee membership information with guidance on what is
expected of committee members.

Author: tautschnig

doc/src/general-rules.md

@@ -92,3 +92,18 @@ members = [
 +   "rahulku"
 ]
 ```
+
+Committee members are expected to contribute by reviewing pull requests (all
+pull requests review approvals from at least two committee members before they
+can be merged).
+Reviews of solutions towards challenges should consider at least the following aspects:
+
+1. Does the pull request implement a solution that respects/meets the success
+   criteria of the challenge?
+2. Do the contracts and harnesses incorporate the safety conditions stated in
+   the documentation (from comments in the code and Rust book)? Note that we
+   currently focus on safety verification. Pre- and post-conditions towards
+   functional correctness are acceptable as long as they do not negatively
+   impact verification of safety, such as over-constraining input values.
+3. Is the contributed code of adequate quality and idiomatic (to the best of the
+   committee member's knowledge).