Global convert to uppercase and lowercase in macOS?
You can do it in Safari, but Chrome ignores the standard Mac Toolbox, unfortunately.  

System Prefs > Keyboard > Shortcuts > App Shortcuts

You can set key commands for All Applications, which will then work for all that have the requisite menu option.

This is my own setup, which shows keys already set for Capitalise &amp; Lower Case
I use it a lot for such as Stack Exchange.