fix(SNOTES-473): code editor fixes

[antsgar]

Fixed errors in code editor:

• Refused to execute inline event handler because it violates the following Content Security Policy directive: "script-src 'self', fixed by removing inline event handlers from the HTML file and setting up event listeners on the JS file instead.
• Refused to execute inline script because it violates the following Content Security Policy directive: "script-src 'self', fixed by moving contents of inline script to JS file.
• Refused to apply inline style because it violates the following Content Security Policy directive: "style-src *"., fixed by setting style in CSS file instead of using inline styling.

This fixes the "Enable Vim mode" button not working, as well as the language dropdown/default language setter button.