Make the usage of letter-casing consistent across Cutter's interface

Is your request related to a problem? Please describe.

The interface of Cutter is full of mixed types of titles that are not unified. Since we don't have guidelines for these, we need to create ones and make sure that the usage of letter-casing in titles is consistent throughout the interface.

Type of casings: all capital (AC) - "RESET SETTINGS" mixed case (MC) - "Export as code" title case (TC) - "Save As..."

In the image, an example of an inconsistent menu:

Describe the solution you'd like

1. Decide on a guidelines based on UX best-practices (and not personal taste of developers)
2. Document the guidelines in the docs for developers
3. Change all the menu items to fit to the chosen decision

Additional context

References:

• Why letter casing is important to consider during design decisions
• Headline Capitalization for UX: Title Case vs. Sentence Case
• A thorough, detailed, comprehensive, methodical guide to capitalizing strings in our user interface
• Collection of Style guides from big companies and organizations