Allow rich text for Developer#bio

[rayhanw]

Allows markdown for developer#bio. Closes #633

Pull request checklist

• My code contains tests covering the code I modified
• I linted and tested the project with bin/check
• I added significant changes and product updates to the changelog

Notes:

• Redcarpet markup can be found here.
• I created a custom renderer object to handle links and images.
  If the user writes a markdown link/image, it will be saved into the DB but rendered as an empty string (check the custom renderer object above). I'm not sure if this is the best way, or whether actually removing it before the bio is saved would be better. Let me know!
• I didn't write tests for the custom renderer object because I'm honestly not sure what to test of it and it should also be covered by the developers/rich_text concern tests.

Examples:

Text:

**Lorem ipsum dolor sit amet.**

Result:

<strong>Lorem ipsum dolor sit amet.</strong>

---

Text:

[link](https://example.com)
![image](https://example.com)

Result:

[link](https://example.com)
![image](https://example.com)

[joemasilotti]

Nice work so far!

I'd prefer to keep all of the user's inputted text for the bio instead of deleting anything. Can we instead render the markup directly, as in not an HTML <a> tag?

It looks like you are already disabling links and images via the HTML renderer. I think that's good enough and exactly what we want!

[rayhanw]

With the chosen options for the renderer and markdown, this is what it looks like now:

Might I also suggest adding in a text in the bio section in the form that says something along the lines of "Markdown is supported".

Should now be ready for review 👍

[joemasilotti]

Excellent! The preview you rendered looks perfect.

Let's add the "Markdown supported" text – great idea. Please use the following copy (it can be added below the EXAMPLE TOPICS list):

Markdown is supported but links and images are removed.

[rayhanw]

It is now just missing non-English translations 🙏

[joemasilotti]

Looks and works great! I only have two tiny requests.

[joemasilotti]

Oh, I just noticed one more thing. Developer cards are rendering the plain markdown. Let's update that to remove the markup tags and render plain text. For example:

**hi** _bye_ should render as:

• hi bye – on the developer profile page
• hi bye – in a developer card

[rayhanw]

Looks like this now on the developer cards (with Redcarpet's stripdown renderer)

[joemasilotti]

This looks great! I made a few tiny tweaks and will merge after CI passes.

Thanks for your contribution, @rayhanw.