Update Gitlab home to align with OSDU comms template

Our Gitlab home is out of date, we need to update it in line with the template provided by comms and confirm with Rachel Attah once complete: https://gitlab.opengroup.org/osdu/member-information/forum-wide-library-resource/-/blob/main/GitLab_Home_README_Standard_Template.docx.

Context: The comms group are leading a dedicated effort to ensure that all working & capability groups, have updated Gitlab Home pages. The aim of the Gitlab home page is to provide new joiners all the necessary info to get plugged into your group and for existing members to have visibility on group activities within the forum. It is linked to the on-boarding effort around the org overview, where all Gitlab homepages are linked: https://osduforum.org/org-chart-for-members/.