docs: create a doc for the help wanted label

Signed-off-by: Tiexin Guo <guotiexin@gmail.com>

docs/development/help-wanted.md

@@ -0,0 +1,16 @@
+# Help Wanted Issues
+
+These issues should be suitable for someone who has either contributed to the project before, or an experienced developer who is comfortable navigating a new codebase.
+
+Items marked with the "help wanted" label should meet the following standards:
+
+- Medium to Low Priority
+- Low barrier to entry: this should be harder than "good first issue," but still, the difficulty should be limited to a reasonable level.
+- Tractable for new contributors. Documentation on how that type of change should be made should already exist.
+- Clearly defined and agreed upon and does not require further discussions. Point it out if that area of code is untested and requires new fixtures. When possible, point to existing code that serves as an example of how to implement the change.
+- API/CLI behavior is decided and included in the original issue, for example: "The new command syntax is dtm xxx NAME [--some-flag] [--timeout 5m]", with expected input validations, output, and error handling defined.
+
+Tips for creating help wanted issues:
+
+- Only select issues that aren't in key pathways, or must be done quickly: you don't want to put effort into grooming these issues, then end up having to do it yourself because it must be done soon.
+- Keep them up-to-date: regularly review these issues, and make sure that they haven't already been implemented, aren't necessary anymore, and the suggested solution or design is still appropriate.

mkdocs.yml

@@ -110,5 +110,6 @@ nav:
     - development/commands/develop*.md
     - development/reviewing*.md
     - development/good-first-issues*.md
+    - development/help-wanted*.md
     - development/branch-and-release*.md
   - Road Map ⧉: https://github.com/devstream-io/devstream/blob/main/ROADMAP.md