Move default fonts to new crate epaint_default_fonts (#4853)

This allows license checking tools to omit the OFL and UFL licenses when
`default_fonts` are turned off.

There was some discussion of versioning on the original issue; I have
chosen to label this version as `0.28.1` to match the other crates.
Happy to adjust the version as needed.

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* Closes <https://github.com/emilk/egui/issues/2321>
* [X] I have followed the instructions in the PR template

---------

Co-authored-by: Alex Pinkus <pinkus@amazon.com>

scripts/generate_changelog.py

@@ -228,6 +228,7 @@ def main() -> None:
         "egui-winit",
         "egui",
         "epaint",
+        "epaint_default_fonts",
     ]
 
     # We read all existing changelogs to remove duplicate entries.