fix: missing requirement (#1896)

## Summary

* Fix missing requirement (needed by
lib/EpdFont/scripts/build-sd-fonts.py)
* Add a root requirements.txt to simplify installation

---

### AI Usage

While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.

Did you use AI tools to help write this code? _**NO**_

lib/EpdFont/scripts/requirements.txt

@@ -1,2 +1,3 @@
 fonttools>=4.62.1
 freetype-py>=2.5.1
+pyyaml>=6.0.3

requirements.txt

@@ -0,0 +1,2 @@
+-r lib/EpdFont/scripts/requirements.txt
+-r scripts/requirements.txt