fix: add Mirror hyperlink (#355)

# What ❔

- Add Mirror hyperlink

## Why ❔

- Increased visibility and community engagement for zkSync Mirror
articles.

## Checklist

<!-- Check your PR fulfills the following items. -->
<!-- For draft PRs check the boxes as you complete them. -->

- [x] PR title corresponds to the body of PR (we generate changelog
entries from PRs).
- [x] Tests for the changes have been added / updated.
- [x] Documentation comments have been added / updated.
- [x] Code has been formatted via `zk fmt` and `zk lint`.

README.md

@@ -41,6 +41,7 @@ at your option.
 - [Twitter](https://twitter.com/zksync)
 - [Twitter for Devs](https://twitter.com/zkSyncDevs)
 - [Discord](https://join.zksync.dev/)
+- [Mirror](https://zksync.mirror.xyz/)
 
 ## Disclaimer