metamask-mobile chore: improve docs after code fence feature

Description

Related issues

Fixes: #160

Manual testing steps

Go to the main README and search for code fence information.

Screenshots/Recordings

N/A

Pre-merge author checklist

[x] I’ve followed MetaMask Coding Standards.
[x] I've clearly explained what problem this PR is solving and how it is solved.
[x] I've linked related issues
[x] I've included manual testing steps
[x] I've included screenshots/recordings if applicable
[x] I’ve included tests if applicable
[x] I’ve documented my code using JSDoc format if applicable
[x] I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.
[x] I’ve properly set the pull request status:
- [x] In case it's not yet "ready for review", I've set it to "draft".
- [x] In case it's "ready for review", I've changed it from "draft" to "non-draft".

Pre-merge reviewer checklist

[x] I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
[x] I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

Nov 20 '23 12:11 Jonathansoufer

CLA Signature Action: All authors have signed the CLA. You may need to manually re-run the blocking PR check if it doesn't pass in a few minutes.

Nov 20 '23 12:11 github-actions[bot]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 41.66%. Comparing base (814e37d) to head (99fb7a0).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7879   +/-   ##
=======================================
  Coverage   41.66%   41.66%           
=======================================
  Files        1271     1271           
  Lines       30906    30906           
  Branches     3088     3088           
=======================================
  Hits        12877    12877           
  Misses      17250    17250           
  Partials      779      779

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