Updated contribution info

CONTRIBUTING.md

@@ -1,5 +1,14 @@
-If you commit changes:
+### If you commit changes:
 
 1. Make sure all tests pass.
-2. Run benchmark, make sure that performance not degraded.
+2. Run `./benchmark/benchmark.js`, make sure that performance not degraded.
-3. DON'T include auto-generated browser & demo files to commit.
+3. DON'T include auto-generated browser files to commit.
+
+### Other things:
+
+1. Prefer [gitter](https://gitter.im/markdown-it/markdown-it) for short "questions".
+   Keep issues for bug reports, suggestions and so on.
+2. Make sure to read [dev info](https://github.com/markdown-it/markdown-it/tree/master/docs)
+   prior to ask about plugins development.
+3. Issues of "question" type are closed after several days of inactivity,
+   if not qualified as bug report, enhancement etc (see 1).