Add an optional arg to current interface to perform certain action on source code ranges.

fn pretty_print(content: &str, width: usize, actions: Vec<(start, end, RewriteAction)>)

, where action is an enum defined in typstyle. It can be ToMultiline, ToSingleLine, ToBlockEquation, ToInlineEquation, NoFormat...

typstyle will find the first ast node(in order traversal) which is contained by the provided range.

When certain action is not applicable, it will be sliently ignored