Enhance Bilibili video support (redo of #2522) (#2599)

* Enhance support for bilibili videos in responsive video helper, and add corresponding doc

* Apply @iBug's review in mmistakes/minimal-mistakes#2522

* Fix danmaku in page hero video

* Update video to use case..when for iframe src

* Update CHANGELOG and history

Co-authored-by: Anran <51769728+ALeafWolf@users.noreply.github.com>
Co-authored-by: Michael Rose <mmistakes@users.noreply.github.com>

docs/_docs/14-helpers.md

@@ -179,6 +179,7 @@ Embed a video from YouTube, Vimeo, Google Drive, or bilibili that responsively s
 | ---------- | ------------ | ---------------------------------------------------------- |
 | `id`       | **Required** | ID of the video                                            |
 | `provider` | **Required** | Hosting provider of the video: `youtube`, `vimeo`, `google-drive`, or `bilibili` |
+| `danmaku`  | Optional     | Bilibili only, [details below](#Bilibili)                  |
 
 ### YouTube
 
@@ -240,6 +241,30 @@ header:
     provider: google-drive
 ```
 
+### Bilibili
+
+To embed the following Bilibili video at url `https://www.bilibili.com/video/BV1E7411e7hC` into a post or page's main content you'd use:
+
+```liquid
+{% raw %}{% include video id="BV1E7411e7hC" provider="bilibili" %}{% endraw %}
+```
+
+If you want to enable danmaku (弹幕) for the embeded video, which is disabled by default, you can supply an additional parameter `danmaku="1"` as shown below: 
+
+```liquid
+{% raw %}{% include video id="BV1E7411e7hC" provider="bilibili" danmaku="1" %}{% endraw %}
+```
+
+To embed it as a video header you'd use the following YAML Front Matter:
+
+```yaml
+header:
+  video:
+    id: BV1E7411e7hC
+    provider: bilibili
+    danmaku: 1
+```
+
 ## Table of contents
 
 Auto-generated table of contents list for your posts and pages can be enabled using two methods.

docs/_docs/18-history.md

@@ -5,7 +5,7 @@ permalink: /docs/history/
 excerpt: "Change log of enhancements and bug fixes made to the theme."
 sidebar:
   nav: docs
-last_modified_at: 2020-07-22T15:36:16-04:00
+last_modified_at: 2020-07-11T12:31:08+08:00
 toc: false
 ---
 
@@ -21,6 +21,7 @@ toc: false
 - Update link to wtfpl license in README. [#2571](https://github.com/mmistakes/minimal-mistakes/pull/2571)
 - Ignore teaser headline in table of contents when including posts list in another page. [#2558](https://github.com/mmistakes/minimal-mistakes/pull/2558)
 - Replace Font Awesome Kits with CSS from jsDelivr CDN. [#2583](https://github.com/mmistakes/minimal-mistakes/pull/2583)
+- Add `danmaku` option to Bilibili video provider and add corresponding documentation/ [#2599](https://github.com/mmistakes/minimal-mistakes/pull/2599)
 
 ## [4.19.3](https://github.com/mmistakes/minimal-mistakes/releases/tag/4.19.3)