docs: improve issue templates (#1235)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

.github/ISSUE_TEMPLATE/step_request.md

@@ -0,0 +1,29 @@
+---
+name: New step request
+about: Suggest a new step/package manager to update
+title: ''
+labels: C-feature request, request step
+assignees: ''
+
+---
+
+## Checklist
+
+- [ ] I have searched the issue tracker for relevant or duplicate issues.
+
+## I want to suggest a new step
+
+* Which tool is this about? Where is its repository?
+* Which operating systems are supported by this tool?
+* What should Topgrade do to figure out if the tool needs to be invoked?
+* Which exact commands should Topgrade run?
+* Does it have a `--dry-run` option? i.e., print what should be done and exit
+* Does it need the user to confirm the execution? And does it provide a `--yes`
+  option to skip this?
+
+## More information
+
+<!-- Assuming that someone else implements the step,
+please state if you know how to test it from a side branch of Topgrade. -->
+
+- [ ] I am able and willing to implement this step myself