Rewrite link reference definitions

[chenzhiguang]

Now it has a clean ParagraphSyntax.

Benchmarks

Before

After

[coveralls]

Pull Request Test Coverage Report for Build 3999639675

• 123 of 124 (99.19%) changed or added relevant lines in 5 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.3%) to 96.017%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib/src/link_parser.dart	94	95	98.95%
<!--	Total:	123	124	99.19%	-->

Files with Coverage Reduction	New Missed Lines	%
lib/src/block_syntaxes/paragraph_syntax.dart	2	86.67%
<!--	Total:	2		-->

Totals
Change from base Build 3999565601:	0.3%
Covered Lines:	1374
Relevant Lines:	1431

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💛 - Coveralls

[chenzhiguang]

@srawlins Hi Sam, please do not forget this one when you have time. And there are some more PRs after it. 🙂

[kevmoo]

@chenzhiguang – just updated your branch w/ my latest change

[chenzhiguang]

@chenzhiguang – just updated your branch w/ my latest change

Thanks. I am just about to do it.

[chenzhiguang]

Awesome! 🥳