docs(example): Add missing DB file to Gravity Forms example

[ahuseyn]

@Fran-A-Dev as a part of #304, I've been testing the examples and I had an issue with your example. It gets stuck at "Loading form..." screen, as in the screenshot. One of the issues is that the example missing the wp-env databse which should include your settings and config on WP.
Would you please take a look at this when you're available?

Originally posted by @ahuseyn in #304 (comment)