Add EIP: NFT Alternative Text in Metadata

[DecoratedWings]

Information Level EIP to suggest alternative text within NFT metadata as a best practice standard for accessibility.
This directly pertains to users who leverage screen readers.

[eth-bot]

File EIPS/eip-7515.md

Requires 1 more reviewers from @axic, @Pandapip1, @SamWilsn, @xinbenlv

[github-actions]

The commit 0660aef (as a parent of 1c6a1a0) contains errors.
Please inspect the Run Summary for details.

[SamWilsn]

I am closing this pull request because we are in the process of separating EIPs and ERCs into distinct repositories. Unfortunately, as far as we are aware, GitHub does not provide any tools to ease this migration, so every pull request will need to be re-opened manually.

As this is a PR to create / modify an ERC, I will kindly ask you to redirect this to the new repository at ethereum/ERCs. We have prepared a guide to help with the process.

If there is relevant history here, please link to this PR from the new pull request.

On behalf of the EIP Editors, I apologize for this inconvenience.