Introduce different blockquote styles for tips, warnings, etc

[gtsiolis]

Problem

Currently, the docs are using the same color and style to indicate tips, warnings, etc. For example, see the security note in Sharing and Collaboration and the note in Docker Configuration.

Also, the same color is used to inject code blocks and inline code which also overlaps with references to user interface elements like buttons (Pull Request, Add single comment, etc.). For example, see Pull Requests or Install on Google Cloud Platform.

Proposal

TBD (To be discussed)

@jankeromnes also proposed we could use emojis to help here, see https://github.com/gitpod-io/website/pull/971#discussion_r566825315.

Alternatively, maybe we could just use different emoji? E.g.

⚠️ Warning: Doing this will delete all your data forever.

💡 Tip: You can also do this other thing that's pretty cool.

📖 Explanation: By doing this, you make Gitpod watch your repository for code changes. Every time a new change is pushed, it will prepare a re-usable workspace snapshot, by building your Dockerfile and init tasks, which will then be used as a base to start new workspaces extremely fast.

[jankeromnes]

Many thanks for opening this follow-up issue!

Another relevant comment: https://github.com/gitpod-io/website/pull/971#discussion_r566658817