Feat(parser): add a file extention property

[takker99]

Proposed Changes

• add the property lang in CodeBlock
• enable to parse filenames like hello.ts(js)

[progfay]

Language of CodeBlock is not simple in Scrapbox.
For example, language of code:cljc is clojure, code:processing is java.

This change only provides the file extension, and property name lang is not suitable.

[takker99]

The behavior of lang is equal to scrapbox.Page.lines, so I thought it was natural to push a file extension into lang.

• For example:
• 
  But I also understand property name lang is not suitable. I'm going to close this PR.

[progfay]

Thank you for your Pull Request!

But, this package will not support for file extensions.
For getting extension of filename in CodeBlock, try to parse filename yourself.
If you use this package in Node.js, path.extname is very useful.

[takker99]

Thank you for your review!

At least I wanted you to implement parsing filenames like script.gs(js) so that I recreated code block URLs easily.
But I understand the reason you will not support file extensions. I'll parse file extensions and script.gs(js) by myself.