docs: add alephao/solidity-benchmarks

[alephao]

Adding alephao/solidity-benchmarks. Which contains benchmarks of popular implementations of ERC20, ERC721 and ERC115 and is being actively maintained.

The educational category seem like the best fit for me, but not sure.

Checklist

• [x] The URL is not already present in the list (check with CTRL/CMD+F in the raw markdown file).
• [x] Each description starts with an uppercase character and ends with a period.
  Example: solc-js - JavaScript bindings for the compiler.
• [x] Drop all A / An prefixes at the start of the description.
• [x] Avoid using the word Solidity in the description.

[bkrem]

Looks great, thank you for adding! 🙌