Broken links review

[LexaMichaelides]

Tracking issue for any broken links or images on the Handbook following our Summary Update push

[LexaMichaelides]

• [x] Remove 'Under Construction' banner: https://handbook.hypha.coop/
• [x] Fix image link to CWCF logo: https://handbook.hypha.coop/Hypha-Worker-Co-operative/co-operative.html
• [x] Bulletin board links (I think the board used to be clickable too): https://handbook.hypha.coop/How-we-work/virtual-office.html

[tripledoublev]

Completed the tasks listed above and created PR #225