feat: add new api (Node::children and Range::extended_by)

[lemonadern]

tree-sitter module にいくつかのAPIを追加しました

tree-sitter like API

• Node::children
• Node::prev_sibling
• Cursor::goto_prev_sibling

cstree の機能のラッパー

• Node::last_token
  • https://docs.rs/cstree/0.13.0/cstree/syntax/type.SyntaxElement.html#method.last_token
• Node::next_token
  • https://docs.rs/cstree/0.13.0/cstree/syntax/struct.ResolvedToken.html#method.next_token
• Node::descendants
  • ResolvedToken::descendants_with_tokens をラップ
  • https://docs.rs/cstree/0.13.0/cstree/syntax/struct.ResolvedNode.html#method.descendants

その他

• Range::extended_by
• Range::is_adjacent