Fix task list rendering (Fix #749)

[jhildenbiddle]

This PR restores the task list presentation removed in 4.8:

• Add “task-list-item” class to task list <li> elms
• Hide list bullets on unordered task lists <li> elms

It also provides several improvements on the pre-4.8 presentation:

• Add “task-list” class to task list <ul> elms
• Display list numbers on ordered task lists <li> elms
• Render accessible task list items by wrapping checkbox and text in <label> elm
• Allow task lists to be nested within standard ordered/unordered lists

Please makes sure these boxes are checked before submitting your PR, thank you!

• Make sure you are merging your commits to master branch.
• Add some descriptions and refer relative issues for you PR.
• DO NOT include files inside lib directory.

[jhildenbiddle]

@QingWei-Li — I suspect this is a general Travis issue and not an actual docsofy build issue. Can we rerun CI to clear this PR for a merge?

[jhildenbiddle]

Excellent!

Thanks, @QingWei-Li.

[timaschew]

Let's create a follow up PR to provide some tests for this feature.

[jhildenbiddle]

@timaschew -- agreed on the need for automated tests, but since docsify has no test framework in place I think testing is a larger conversation to be handled separately.

Let's move the discussion to #386 and decide how to move forward.

[timaschew]

Actually, I've created it: #760
It's not End2end but I think this is better than nothing.

[jhildenbiddle]

Awesome! Didn't see that PR. Thanks for the follow-up, @timaschew!

[timaschew]

ping @jhildenbiddle

[jhildenbiddle]

Whats up, @timaschew?

[timaschew]

Do you see my comments regarding the start argument?
https://github.com/docsifyjs/docsify/pull/757/files/1c9ce150576d272b21c162c344b8b9bb1651ed2f#diff-d73f215ac772d2673dd8c51f24976e4e

[jhildenbiddle]

Weird. I'm not seeing any comments by following the link or manually navigating to the "Files Changed" tab. Maybe they aren't showing because the PR has already been merged?

Since I can't see the comment I don't know what the concern is, but if it has to do with the argument name I thought I'd mention that I'm using the same argument names listed on marked.js.org (see "Block level renderer methods" > "list(string body, boolean ordered, number start)").

[timaschew]

That's really weird, it's even shown to me on this page, here is a screenshot:

[jhildenbiddle]

Weird indeed. Attached is a full-page screenshot from my view:

Anyway, the start argument allows an ordered list to begin with a number other than 1. A sample block of markdown you can use to test is as follows:

1. One
2. Two

Text

3. Three

Docsify should render the following HTML:

<ol>
  <li>One</li>
  <li>Two</li>
</ol>
<p>Text</p>
<ol start="3">
  <li>Three</li>
</ol>

Notice the start attribute on the second <ol> element.

[timaschew]

Ah, got it, thanks for clarification!
I've extended the tests.

[jhildenbiddle]

Excellent. Thanks for taking on the testing task, @timaschew. Hopefully we can get others to follow suit.