odoo_repository add readme

[hparfr]

A human readable readme of the module can help users to figure out what a module is about.

Plan to:

• add readme as field into odoo_repository/models/odoo_module_branch.py (and in views)
• parse readme.md or readme.rst or static/index.html in odoo_addons_analyzer/module.py

[github-actions]

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