When encountering a " or a ', returns the whole string, including the quote characters.
The entry point to parse the CSS rules. Every time we encounter a {, we then parse the rules
inside it.
Returns a CSS property name. Ends when encountering a : character.
Try to get the value of a CSS property (the #fff in color: #fff). It’ll stop when it
encounters a { or a ; character.
This is used to parse inside a CSS {} block. If we encounter a new { inside it, we consider
it as a new block and therefore recurse into parse_rules.
Skips a /* comment.
Skips a line comment (//).