docs: Add signals to list of projects using Melos (#754)

<!--
  Thanks for contributing!

Provide a description of your changes below and a general summary in the
title

Please look at the following checklist to ensure that your PR can be
accepted quickly:
-->

## Description

<!--- Describe your changes in detail -->

## Type of Change

<!--- Put an `x` in all the boxes that apply: -->

- [ ] ✨ `feat` -- New feature (non-breaking change which adds
functionality)
- [ ] 🛠️ `fix` -- Bug fix (non-breaking change which fixes an issue)
- [ ] ❌ `!` -- Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] 🧹 `refactor` -- Code refactor
- [ ] ✅ `ci` -- Build configuration change
- [ ] 📝 `docs` -- Documentation
- [ ] 🗑️ `chore` -- Chore

packages/melos/README.md

@@ -156,6 +156,7 @@ The following projects are using Melos:
 - [ubuntu/app-center](https://github.com/ubuntu/app-center)
 - [jhomlala/alice](https://github.com/jhomlala/alice)
 - [powersync/powersync.dart](https://github.com/powersync-ja/powersync.dart)
+- [rodydavis/signals.dart](https://github.com/rodydavis/signals.dart)
 
 > Submit a PR if you'd like to add your project to the list. Update the
 > [README.md](https://github.com/invertase/melos/edit/main/packages/melos/README.md)