Example of modifying an AST

[abhillman]

Description

Some basic code that demonstrates modifying an AST.

Considered alternatives

Poking around, playing with various things, reading tests -- currently doing that.

Additional context

An example could look something like this:

fn main() {
    let parse: rnix::Parse<rnix::Root> = rnix::Root::parse("\"hello world!\"");
    if !parse.errors().is_empty() { panic!(); }
    let syntax_node: rnix::SyntaxNode = parse.syntax();
    // modify the ast and call `println!("Modified: {}", syntax_node_modified);`
    println!("Original: {}", syntax_node);
}

[abhillman]

Related #151 (comment)

[oberblastmeister]

rust-analyzer has a good example for this https://github.com/rust-lang/rust-analyzer/blob/master/crates/syntax/src/ted.rs

I wonder if we should add an interface like that.

An example to modify the syntax tree would also be nice.