I love this! Thank you soooooo much!
The easiest way I've found for a global association is simply to Ctrl+Shift+P and type "change language mode" with a file of the type you're associating open.
In the first selections will be the option "Configure File Association for 'x' " (whatever file type - see image attached). Selecting this gives you the option to choose the language and will then make the filetype association permanent.