Backfill the CHANGELOG for 0.10.0

CHANGELOG.md

-Nothing to see here...
+## Version 0.10.0
+
+**User improvements:**
+
+- New packages: `html5lib`, `pygments`, `beautifulsoup4`, `soupseive`,
+  `docutils`, `bleach`
+
+**Developer improvements:**
+
+- `console.html` provides a simple text-only interactive console to test local
+  changes to Pyodide. The existing notebooks based on legacy versions of Iodide
+  have been removed.
+
+- The `run_docker` script can now be configured with environment variables.