[README] Add GitPOAP Badge to Display Number of Minted GitPOAPs for Contributors

[burz]

Description

Hey all, this PR adds a GitPOAP Badge to the README that displays the number of minted GitPOAPs for this repository by contributors to this repo.

You can see an example of this in our Documentation repository.

This should help would-be contributors as well as existing contributors find out that they will/have received GitPOAPs for their contributions.

CC: @colfax23 @kayla-henrie

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• [x] I have selected the correct base branch.
• [x] I have performed a self-review of my own code.
• [x] I have commented my code, particularly in hard-to-understand areas.
• [x] I have made corresponding changes to the documentation.
• [x] My changes generate no new warnings.
• [x] Any dependent changes have been merged and published in downstream modules.
• [x] I ran npm run dtslint with success and extended the tests and types if necessary.
• [x] I ran npm run test:cov and my test cases cover all the lines and branches of the added code.
• [x] I ran npm run build with success.
• [x] I have tested the built dist/web3.min.js in a browser.
• [x] I have tested my code on the live network.
• [x] I have checked the Deploy Preview and it looks correct.
• [ ] I have updated the CHANGELOG.md file in the root folder.

Question: I would assume CHANGELOG.md would not need to be updated for this small README change? I will update the PR if I should still go ahead with it. Thanks!