Code coverage support

[froozeify]

This PR add code coverage support for plugin.

By default the coverage is not enabled.

For a better output, plugin can extract the report to automatically create a comment on the PR with the report in md format.

Interconnected PR :

• Code coverage support #49
• ci: add code coverage support pluginsGLPI/empty#56

Whatsapp plugin got a dedicated PR to test the modification (see in the feed under for the link)

[Rom1-B]

For activation, I think we need to follow the same logic as the other steps and test for the presence of the configuration file instead of defining a variable.

Suggested change

	if: ${{ !cancelled() && inputs.code-coverage == true }}
	if: ${{ !cancelled() && hashFiles(format('{0}/cobertura.xml', inputs.plugin-key)) != '' }}

Same logic every time you test inputs.code-coverage == true

[froozeify]

We should create a dedicated config file. For example .glpi-coverage.json

If the file is not present or if his field enabled is false we don't run code coverage.

Enabled field is optional, value is true by default. For glpi-empty, we would be able like that to set it has example with enabled: false

This file would should contain something like

{
  "enabled": true,
  "lower_threshold": 50,
  "upper_threshold": 75,
  "fail_below_min": false
}

We should probably also create a generic action for the code coverage report config in that case. (if feasible)
This will avoid to have to put that config on every plugin : https://github.com/glpi-network/whatsapp/pull/32/changes#diff-c471496bcb3ed47397b73d2e3e3aa41a8a679c86accaed9e05676fd9d5987434R41-R70