Typo and syntax fixes in the README

[humantree]

• Fixed a couple of typos in the rebuild-roms section
• Fixed the option blocks that didn't have their syntax highlighting working correctly when they were coming directly after a list

[alucryd]

Thanks for the fixes! Could you please target develop instead of master? Shouldn't need any code change. That way I won't have to cherry-pick it in develop as well and it will be merged with my next changes.

[humantree]

@alucryd Done!

[alucryd]

Thanks!