Add a simple helper script to build full set of material icons as msdf

[mikenye]

The script:

• Creates (and cleans up) the neccessary folder structure
• Downloads the MaterialIcons-Regular TTF and codepoint definitions
• Builds charset.txt from codepoint definitions
• Runs generators/msdf/main.go to generate the MSDF
• Copies output files into src/editor/editor_embedded_content/editor_content/fonts/