This is built in to NVDA itself, under the NVDA Help Menu. If you hit NVDA+N,H,Q (NVDA Main Menu, Help Submenu, Commands Quick Reference) you'll be presented with the long list of the most commonly used key commands, including reading commands, in whatever web browser you have set as your default.
Also take a look at the other options under the Help Submenu.
Brian - Windows 10 Pro, 64-Bit, Version 2004, Build 19041
A gentleman is one who never hurts anyone's feelings unintentionally.
~ Oscar Wilde