Add case insesitivity about switch.vim

[AndrewRadev]

Would this functionality work for your use cases?

switch.vim/doc/switch.txt

Lines 187 to 201 in ec2b710

	You might want this to work for different capitalizations, like with `true`
	and `True` and `TRUE`. While you could use the more complicated dict
	definition, a simple way to tackle this is to use the `switch#NormalizedCase`
	helper:
	>
	let g:switch_custom_definitions =
	\ [
	\ switch#NormalizedCase(['one', 'two'])
	\ ]
	<
	This would switch between "one" and "two", between "One" and "Two", and
	between "ONE" and "TWO". This is not the default, since you might want to
	change casing in your switches. See |switch-internals| for some information on
	the underlying data format if you'd like to use a different method to
	generate definitions (like, say, loading JSON).

For longer explanations on casing, take a look at #28 and/or #1 (comment)

[wsistyrud]

That was exactly what I was looking for. Thank you!