feat: support more foldable AST nodes

[Myriad-Dreamin]

Previous, they are:

• content blocks, e.g. [ .. ]
• code blocks, e.g. { .. }
• heading elements, e.g. == Heading

This PR adds more markups to fold:

• equations, e.g. $ .. $
• raw blocks, e.g. ` .. `
• block comments, e.g. /* .. */

This PR adds more expressions to fold:

• parenthesized expression, e.g. ( 1 + 2 )
• destructuring pattern, e.g. left side of (a, b) = (c, d)
• argument list, e.g. the brace in f(a, b)
• array, e.g. (c, d)
• dictionary, e.g. (c: d)