Add "flow" vscode language

[mroch]

We're considering having flow-for-vscode register a separate VSCode language for "flow" and it'd be great if this extension supported it too.

vscode-language-babel/package.json

Lines 14 to 21 in 6679732

	"activationEvents": [
	"onLanguage:javascript",
	"onLanguage:javascriptreact",
	"onLanguage:jsx",
	"onLanguage:jsx-attr",
	"onLanguage:styled-css",
	"onCommand:javascript.reloadProjects"
	],

As long as there are no objections I'll send a PR around the time we change this in flow-for-vscode.

ref flow/flow-for-vscode#187

[michaelgmcd]

I'm open to the idea. A little worried about the added support required for a separate VSCode language, but I think it makes sense.