docs(examples): add colors_rgb example

[joshka]

Helpful for diagnosing what's happening with #475

[codecov]

Codecov Report

Merging #476 (37f0194) into main (0c68ebe) will not change coverage.
Report is 2 commits behind head on main.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #476   +/-   ##
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  Coverage   90.06%   90.06%           
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  Files          40       41    +1     
  Lines       11166    11166           
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  Hits        10057    10057           
  Misses       1109     1109           

see 2 files with indirect coverage changes

[kdheepak]

Do you think this should just be a separate demo?

[joshka]

Do you think this should just be a separate demo?

Yes probably. I wasn't sure about it myself, so just went with adding code, but it wouldn't hurt.

[orhun]

Works great!

It isn't really intuitive from the demo so I'd also say that we should have this as a separate example.

[joshka]

I tweaked a bunch of stuff in the updated example:

• Modified color grid to be smooth by mirroring blue channel every 16 pixels instead of starting at 0
• Changed to buf.cell_mut() this is noticeably faster to render than using Paragraph
• App-ified and Widget-ified implementation
  • Removed manual Error printing (returning Result<()> handles this automatically)
  • panic hook and Drop impl (because I kept getting index out of bounds errors when playing around with generating the grid)
• Simplified everything as much as possible

[joshka]

• Added example to cargo toml and fixed commit message

[joshka]

moved the init/restore/panic hook to the bottom of the file to make the example really hyper focus on the application logic and example rather than the generic terminal parts.