Formatting changes to store.md file for clarity.

[jeremiah]

Added a note about needing a Postgres user and db.

[stappersg]

Please put the

If you decide to use PostrgreSQL instead of the default RocksDB, you'll need to add a user and a database into PostgreSQL before Stalwart can add data to it.

on a fresh line. (Don't make the looonnggg line even looooonngerrrrrr.)

[jeremiah]

Added a new line.

[stappersg]

Please drop the extra trailing space.

And pretty please: Make the commit only adding the new line. In other words: only green in this commit

Regards
Some fellow stalwart fanboy

[jeremiah]

I think I've done that. I'm using the GitHub interface so it is not producing a similarly colored diff as yours. I can switch to the command line if needed. I've also clicked the button that allows reviewers to edit diffs.

Cheers,

Jeremiah