Correctly integrate "Ekko" (our polar bear) in the rule description

[jhertout]

Ekko our polar bear is a fun "plus" in our rules description that helps us to be identified. However the face of Ekko must match the severity of the rule and it is not always the case. Here is the image that must be used in the description depending on the severity:

Ekko	SonarQube 9 severity	SonarQube 10 severity
	Blocker, Critical	High
	Major	Medium
	Minor, Info	Low

For the moment, Ekko's pictures are on a Snapp' server not really done for that. We must clean this before modifying the rules description.
We must see how to integrate this with the ecoCode centralized rule system too.

Ekko's picture are available here if necessary:

ecoCode.zip