Add TEAM Engine documentation to TEAM Engine landing page

[dstenger]

Currently, the landing page is available here: https://cite.opengeospatial.org/teamengine/
And the documentation here: https://opengeospatial.github.io/teamengine/
Shall be similar to the documentation of the test suites: https://cite.opengeospatial.org/teamengine/about/wfs/2.0.0/site/

So, the documentation shall be provided via the TEAM Engine webapp.

[dstenger]

CITE status meeting 2022-03-24:

• Link to https://opengeospatial.github.io/teamengine/ shall be added to https://github.com/opengeospatial/teamengine-site (Beta and Production) so that a user can access the documentation from the landing page.
• Following sentence shall be added:
  • The source of the engine and the tests are available at GitHub. The documentation of the engine is available here(link). The CITE forum provides a place to ask questions and help developers pass the tests.

[bpross-52n]

Done for the beta site: opengeospatial/teamengine-site@0d6e18e