Add a text feature to quickplot

[ESadek-MO]

🚀 Pull Request

Description

Closes #6247

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 89.88%. Comparing base (9442894) to head (0ea6a8b).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/iris/quickplot.py	87.50%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6333   +/-   ##
=======================================
  Coverage   89.88%   89.88%           
=======================================
  Files          88       90    +2     
  Lines       23430    23470   +40     
  Branches     4361     4362    +1     
=======================================
+ Hits        21059    21096   +37     
- Misses       1644     1646    +2     
- Partials      727      728    +1     

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