chore(explorer): Add Gitcoin to the Issuer list (for the Sovs.xyz initiative)

[alainncls]

What does this PR do?

Adds Gitcoin as an Issuer on the Explorer homepage

Related ticket

Fixes #842

Type of change

• Chore
• Bug fix
• New feature
• Documentation update

Check list

• Unit tests for any smart contract change
• Contracts and functions are documented

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 48.59%. Comparing base (251a440) to head (1ba51b6).
Report is 1 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #843   +/-   ##
=======================================
  Coverage   48.59%   48.59%           
=======================================
  Files          18       18           
  Lines         391      391           
  Branches       63       63           
=======================================
  Hits          190      190           
  Misses        198      198           
  Partials        3        3           

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[github-actions]

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