Allow building as normal Arduino project

[adammhaile]

@chamnit & @bdurbrow
As discussed in #715 this is all that's needed to build Grbl as a normal "sketch".
Saw no reason to remove grblUpload at the moment as it's still valid and none of this breaks being able to use it as a library. However, if this was accepted and you wanted to make it the normal way of using Grbl I'd be happy to update the docs to reflect this method.

[Quas7]

Quickly tested this. Works and compiles with Arduino IDE 1.8.9 and 1.8.10 (win-x64).

[zdenekkarny]

Hi,

You can create an empty file "gbrl.ino" on the "gbrl" directory and run it as normal sketch. The skectch file "gbrl.ino" load "gbrl.h" by defafult!

Zdenek

[drf5n]

Adding this grbl.ino file in the directory with the rest of the files works great.

[drf5n]

Note that you can even have an empty grbl.ino file -- This works just as well to make grbl.ino compile in the Arduino IDE:

mkdir GRBLTEST
cd GRBLTEST
git clone git@github.com:gnea/grbl.git
touch grbl/grbl/grbl.ino