Update examples, implement set_root_folder

[ttytm]

This PR

• Updates and formats the examples. Styles are updated as they were done here: https://github.com/webui-dev/webui/pull/175
• Implements webui_set_root_folder as V function
• Updates the text-editor and serve_a_folder examples to be executable independent of the directory. This fixes an error when the examples are not executed from the examples directory itself.
• Renames the hello_world.v example to simple_example.v since it didn't do a lot of hello world related things. Please suggest better names if desired.