Add text.md to grammars list

[twellspring]

Enable spelling for the language-markdown language, which replaces language-gfm.

[bbodenmiller]

I'm already getting spell check with .md it seems. See #144.

[twellspring]

Spell checking only worked for me if I had Github Markdown as the type for my .md files. When I disabled Github Markdown and used only the default Markdown as the type for my .md files I did not get spell checking.

Since Markdown is now the default with a new Atom install, it is likely that new users will not have the GHM installed. Adding the text.md to the default list will provide spell checking for these new users by default while leaving the legacy sources.gfm in the list means existing users using Github Markdown will keep the spell check functionality.

[winstliu]

Since Markdown is now the default with a new Atom install

Can you clarify? GitHub Markdown is still the default (and Markdown is not installed with Atom). How are you installing Atom?

[twellspring]

I am running it on MacOS ... Think I downloaded the zip file from the atom homepage, but not totally sure. I would have to try to re-construct a debugging session to find where I read about language-gfm not being the default any more. if language-gfm is really still the default then the reason to do this pull request would be to allow uses with only language-markdown to get spell check by default.

[burodepeper]

As the author of language-markdown I wanted to submit this path too (as a result of burodepeper/language-markdown#134), so I'm just here giving this my 👍.

#144 seems an equally valid solution, though I prefer the text.md scope.

[twellspring]

Looks like this is not going to get approved/merged so I am closing