Update slack link

[colinepiloquet]

Signed-off-by: Coline Piloquet coline.piloquet@rte-france.com

Please check if the PR fulfills these requirements (please use '[x]' to check the checkboxes, or submit the PR and then click the checkboxes)

• [x] The commit message follows our guidelines
• [ ] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)

Does this PR already have an issue describing the problem ? If so, link to this issue using '#XXX' and skip the rest No

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...) Add the link to the slack in the ReadMe