Fix backslash before closing quote parsing issue

[chelog]

Fixes edge case with value ending with a backslash, even escaped:

"UserLocalConfigStore"
{
	"friends"
	{
		"9734658" "Grocel"
		"5318652" "/Hexalitos\\" <-- this one
		"19358028" "put in"
	}
}

SyntaxError: VDF.parse: invalid syntax on line 8:
"

As an additional bonus, adds strict comparison in this line where it's appropriate