feat: Add range to nodes and fix whitespace issue (fixes #137)

[nonara]

Abstract

It turns out that other AST parsers do create a TextNode for all whitespace (see https://astexplorer.net) The only which does not is the parser for angular templates, which it likely does because it's used in a very narrow context.

The issue ended up being that node-html-parser actually does create a TextNode for whitespace, but there were some cases in which that was failing to happen. This caused the behaviour to differ from other parsers and is the root of the issue laid out in #137.

Features / Fixes

• Added range property to nodes
• Fixed whitespace not being created issue (solves #137 & #126)

Code Changes

• Cleaned up parser code to make it understandable and slightly more efficient
• Added comprehensive test for node ranges
• Added basic whitespace parser test

Version

v4.1.0

Because a feature was added, I recommend bumping minor version.

Related

• 126

• https://github.com/crosstype/node-html-markdown/issues/16

• 137

[nonara]

@taoqf Ready for review!

[taoqf]

Thank you.