patch: work around pip's secure-install bug; bump version

- upstream issue: https://github.com/pypa/pip/issues/9644
- runs tests within a container, uses the same `dockerfile`
- ignores `pdm.lock`, removes `requirement.txt`
- update manual contribution steps
- bumps project version

**Related Items**

_Issues_

- Closes #137

pyproject.toml

@@ -4,7 +4,7 @@
 
 [project]
 name = "waka-readme"
-version = "0.2.2"
+version = "0.2.3"
 description = "Wakatime Weekly Metrics on your Profile Readme."
 license = { text = "MIT" }
 readme = "README.md"