Create mgfx0001.md

[dellis1972]

Add an Error page for the first coded MonoGame error. MGFX0001.

The error codes should be prefixed with the TOOL or assembly which is being used. This will allow us to identify error areas easily.

e.g

mgfx : MGFX
mgcb: MGCB
MonoGame : MG
Content Pipeline: MGCP

I chose a 4 digit code as that should give us enough room to add as many errors (or warnings) as we need.

In this case we want a page with details on WHAT the error is and then a Solution section on how to fix it.

That said we can also use redirects if need be.

[SimonDarksideJ]

@dellis1972 Did you want to access this via:

• https://docs.monogame.net/errors/mgfx0001.html

or

• https://docs.monogame.net/errors/mgfx0001