Use simple markdown to render some responses in a nicer way

[bbondy]

We need simple markdown being used to make responses like this look a lot better.

• Do we need any prompt changes?
• What do we do for code formatting, can we do something similar?

[petemill]

• Tables
• Headings
• Bold, Italic
• Indentation for lists (bullet / numbered)

Headings should allow inline code strings but not code blocks.
Mardown shouldn't be parsed inside code blocks.
Possibly we shouldn't allow links to get made in to an <a>.
We definitely shouldn't allow html, embeds, etc.

[aguscruiz]

Designs here:
https://www.figma.com/file/m0Gdbf0wtqyfEFGm32VLLc/Leo?type=design&node-id=2357%3A50102&mode=design&t=DsCs9Cm1dcjcjbBx-1

Full list of planned content types
https://www.figma.com/file/m0Gdbf0wtqyfEFGm32VLLc/Leo?type=design&node-id=15%3A17545&mode=design&t=DsCs9Cm1dcjcjbBx-1

[stephendonner]

Verification PASSED using

Brave | 1.67.52 Chromium: 124.0.6367.91 (Official Build) nightly (64-bit)
-- | --
Revision | a368a1ab342f0a5d4dee4db3f2699f7d02579247
OS | Windows 10 Version 22H2 (Build 19045.4355)

Case 1: Ensure Correct Rendering

Code blocks ✅

Prompt: write me a finite state machine using C++

Prompt: can you help me write HTML code which outputs a table with 3 columns and two rows?

example	example

Inline code ✅

{Paragraphs (p), Bold text, Heading, Lists} ✅

example	example

Numbered ✅

example	example

Bulleted ✅

Case 2: Ensure the following are NOT rendered

{Links, Tables, Images} ✅

Prompt: what does Superman look like? Can you provide me with an image?

Case 3: Ensure the typing cursor is visible with paragraphs and lists

Caret/Typing cursor ✅

[Uni-verse]

Verified on Samsung Galaxy S21 using version:

Brave	1.67.98 Chromium: 125.0.6422.112 (Official Build) beta (64-bit) 
Revision	9434daa5e8d2aceabb9cce574ab39429f2923b9b
OS	Android 13; Build/TP1A.220624.014; 33; REL

• Verified all output/cases mentioned in the test plan in AIChat: markdown support brave-core#23053 (comment)
• Verified output using all available models.

Correct Rendering

• Code blocks
• Inline code
• Paragraphs (p)
• Bold text
• Headings
• Lists

Example	Example	Example	Example	Example

Not Rendered

• Tables
• Links
• Images

Example	Example	Example