Add font

[frederik-uni]

make it easier to add fonts.

For example if I want to add a custom FontFamily or if the user wants to add a Chinese fallback

• [x] I have followed the instructions in the PR template

[github-actions[bot]]

Preview available at https://egui-pr-preview.github.io/pr/5228-add-font Note that it might take a couple seconds for the update to show up after the preview_build workflow has completed.

[frederik-uni]

@emilk the changes you requested were made

[emilk]

thanks!