Improve Manpage.sublime-syntax, Fix #2353

[Freed-Wu]

It still exists many problems, such as man fzf

Should we highlight +x before or? Case-XXX shouldn't be highlighted, right?

Wrong N[,...].

How to distinguish the following -.s?

[keith-hall]

It would be great to add some "highlighted file" tests for this. Basically just putting man fzf into a file in https://github.com/sharkdp/bat/tree/master/tests/syntax-tests/source/Manpage and running https://github.com/sharkdp/bat/blob/master/tests/syntax-tests/update.sh afterwards and including both files in the PR. This will enable us to see how future changes affect the highlighting, to help prevent regressions.

[Freed-Wu]

It would be great to add some "highlighted file" tests.

Done.

[keith-hall]

Looks good. You can also optionally update the changelog so others will know what you fixed :)

[Freed-Wu]

update the changelog

Fixed.