Document haskell formatter

[leg7]

I spent quite a bit of time making a formatter for ghci (the haskell repl) and I imagine a lot of people are just going to give up trying to make REPLSendVisual work. I think documenting it as an example in the add your own repl or faq section would be very helpful.

Here's what I made:

-- to send a multiline function declaration to ghci you need to
-- surround it like so:
-- 	:{
-- 	code here
-- 	more code
-- 	:}
-- this function formats your visual selection to send it to ghci
function sendLinesGhci(lines)
	local i = 1
	local e = #lines

	while i <= e do
		while lines[i] == '' do
			i = i + 1
		end

		-- If there's more than 1 non empty line left
		if i < e then
			table.insert(lines, i, ':{')
			i = i + 1
			e = e + 1

			while i <= e and lines[i] ~= '' do
				i = i + 1
			end

			table.insert(lines, i, ':}')
			i = i + 1
			e = e + 1
		else -- if there's only 1 left skip it to end the loop
			i = i + 1
		end
	end
	table.insert(lines, '\n')

	return lines
end

local yarepl = require 'yarepl'
yarepl.setup {
	wincmd = 'vertical topleft 80 split',
	metas = {
		ghci = { cmd = 'ghci', formatter = sendLinesGhci },
	},
}

if you want I can make a pr updating the readme.

[milanglacier]

Thanks for your contribution. You can create a PR and point the solution to this issue. I would happy to merge.