Embed videos to pages

[darwintree]

Describe the feature or improvement 描述新特性或改进
Currently, there are some videos made for the documentation portal. We could embed videos in the pages.

Optional: Implementation ideas 可选：如何实现
We could use docusarus tab feature and stream media iframe link to complete the feature.

<Tabs>
  <TabItem value="youtube" label="Video source: youtube">
    <!-- insert youtube iframe link here -->
  </TabItem>
  <TabItem value="bilibili" label="Video source: bilibili">
    <!-- insert bilibili iframe link here -->
  </TabItem>
</Tabs>

The iframe link could be found in share -> embed for both youtube and bilibii. BTW, it should be noted that the bilibili video will be autoplayed for the default copied link. You should add &autoplay=0 after the url.

Example outcome:

• I'd be willing to contribute this feature myself. 我将自己实现这个feature

[darwintree]

An independent page for video? Or sidebar

[0xn1c0]

Added Nodes Video Tutorial at docs/general/run-a-node/

#308

[0xn1c0]

Added videos to existing pages on this PR: #362

The creation of new pages is still pending. Next step is creating new pages in which to add the videos are weren't embedded yet.

[0xn1c0]

Another video was added on this PR: #392

[0xn1c0]

More videos added on this PR: #404