chore: Add doc for how to rotate gitlab token (runatlantis#5290)

Signed-off-by: Luke Massa <lukefrederickmassa@gmail.com>
Signed-off-by: Petr Bubenik <petr.bubenik@drmax.eu>

e2e/README.md

@@ -0,0 +1,15 @@
+# End to end tests
+
+Tests run against actual repos in various VCS providers
+
+## Configuration
+
+### Gitlab
+
+User: https://gitlab.com/atlantis-tests
+Email: maintainers@runatlantis.io
+
+To rotate token:
+1. Login to account
+2. Select avatar -> Edit Profile -> Access tokens -> Add new token
+3. Create a new token, and upload it to Github Action as environment secret `ATLANTIS_GITLAB_TOKEN`.