Migrate InlineDiffFilter to comrak

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InlineDiff is a very straightforward filter that converts any content in {+ ... +} and {- ... -} tags to text highlighted in green or red. However, since its just a filter and not natively supported by the parser, it does not behave like other marks, like bold.

A comparison between bold and inline diff:

Case	Bold		Inline Diff
	Markdown	Output	Markdown	Output	Expectation
Multi-line support	**bold in two lines**	bold in two lines	{+inline diff in two lines+}	{+inline diff in two lines+}	inline diff in two lines	❌
Mixing with other marks inside the current mark	**_bold italic_**	bold italic	{+_italic diff_+}	{+italic diff+}	italic diff	❌
Mixing with other marks outside the current mark	_**bold italic**_	bold italic	_{+italic diff+}_	italic diff	italic diff	✅
Source maps	Supported		Not supported			❌