ci: Introduce .gitlab-ci.yml to integrate with Gitlab Pages

For now we will be only building and deploying the documentation for the
v0.1.1 release.

Issue-Id: SCM-3318
Signed-off-by: Diego Sueiro <diego.sueiro@arm.com>
Change-Id: I2a3f3985edff778ce0d6182fd1e57b1ade2e5070
2 jobs for v0.1.1 in 29 seconds (queued for 35 minutes and 8 seconds)