feat(docs): update footer logo, year, and add LinkedIn link

[Shubham-Jain52]

Closes #5264

Proposed changes

This PR updates the footer section on the Litmus Experiments Docs homepage (/litmus/mkdocs/overrides/home.html) as requested in issue #5264:

• Replaced the old Litmus logo with the new one.
• Updated the copyright year to 2025.
• Added a LinkedIn icon and link to the "Follow Us On" section.

Types of changes

What types of changes does your code introduce to Litmus? Put an x in the boxes that apply

• New feature (non-breaking change which adds functionality)
• Bugfix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices applies)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I have read the CONTRIBUTING doc (Assuming you have)
• I have signed the commit for DCO to be passed. (Make sure you did this, e.g., git commit -s -m "...")
• Lint and unit tests pass locally with my changes (Assuming mkdocs serve worked without errors)
• I have added tests that prove my fix is effective or that my feature works (if appropriate) (Not applicable for this HTML change)
• I have added necessary documentation (if appropriate) (This IS the documentation update)

[PriteshKiri]

Can you please add width of 22px in this, else it will break the footer?