Markdown cleanup

[dmadison]

I went through the various markdown files and cleaned up formatting and language.

• FAQ: Grammar fixes, and added spaces to make it easier to read.
• List of Materials: Fixed the header markdown, and converted all lists to tables
• README: Added link to firmware, matching the other list links.
• ThorBuilders: Converted list to table, and sorted by build status.
• modifications/README: Grammar fixes.

[AngelLM]

Thanks for the fixes!