feat(materials): Support Gitlab security report materials (#1339)

Signed-off-by: Jose I. Paris <[email protected]>

Author: jiparis

README.md

@@ -134,6 +134,7 @@ Chainloop supports the collection of the following pieces of evidence types:
 - [CSAF Informational Advisory](https://docs.oasis-open.org/csaf/csaf/v2.0/os/csaf-v2.0-os.html#43-profile-3-informational-advisory)
 - [CSAF Security Advisory](https://docs.oasis-open.org/csaf/csaf/v2.0/os/csaf-v2.0-os.html#44-profile-4-security-advisory)
 - [CSAF VEX](https://docs.oasis-open.org/csaf/csaf/v2.0/os/csaf-v2.0-os.html#45-profile-5-vex)
+- [Gitlab Security report](https://docs.gitlab.com/ee/user/application_security/)
 - Attestation: existing Chainloop attestations.
 - Artifact Type: It represents a software artifact.
 - Custom Evidence Type: Custom piece of evidence that doesn't fit in any other category, for instance, an approval report in json format, etc.