docs: Enhance "Contribute" section and console-sessions.
build: Improve Eclipse build and build-instructions.

* ci: Rely on python.cfg for running coverage report.
* docs: readme: Mention LiClipse and fix admonitions in lists, etc.
* docs: Enhance python-usage console-sessions.
* build: Use 'wltp.venv' eclipse-interpreter.
* build: Add jsonpointer in deps (for cmdline).