Improve README instructions for a more welcoming onboarding experience

[ThomasCarney315]

@IreneLinWasHere Maybe you can include a tip to remember to click the "update user" button when you need to change the password for DB connection string. This really messed me up 😅

[IreneLinWasHere]

Sure, no problem!

I added the following to step 6:

"Tip: should you need to update a database user, please remember to click the green button that says "Update User" to save your changes."

Do you think that sounds clear?

[ThomasCarney315]

Perfect!