Add signed release tags information for 2.0.0

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>

releases/2.0/2.0.0/index.rst

@@ -11,6 +11,8 @@
 
 **Release Artefacts Download Area**: https://download.eclipse.org/oniro-core/releases/2.0.0/
 
+**Release Tags GPG Public Key**: https://download.eclipse.org/oniro-core/releases/2.0.0/oniro-2.0.0_gpg_key.asc [*]_
+
 .. toctree::
    :maxdepth: 1
    
@@ -19,3 +21,7 @@
    test_report
    ip_compliance_note
    security_report
+
+.. [*] All repositories released part of 2.0.0 have associated 2.0.0 `git
+   tags` that have been signed during the Eclipse Foundation release process.
+   You can use this GPG public key to verify all these signatures.