Improve work with themes in Field and PureField

[vjik]

Q	A
Is bugfix?	✔️
New feature?	✔️
Breaks BC?	❌
Fixed issues	-

[codecov]

Codecov Report

Attention: 92 lines in your changes are missing coverage. Please review.

Comparison is base (8f0b21c) 95.71% compared to head (71fbdab) 94.30%.

Files	Patch %	Lines
src/PureField.php	0.00%	92 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #279      +/-   ##
============================================
- Coverage     95.71%   94.30%   -1.42%     
  Complexity      847      847              
============================================
  Files            52       52              
  Lines          2451     2510      +59     
============================================
+ Hits           2346     2367      +21     
- Misses          105      143      +38     

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[what-the-diff]

PR Summary

This Pull Request primarily focuses on the enhancement of our platform's flexibility to support multiple themes. Here are the major modifications:

• Enhanced Theme Flexibility
  The Field class has been enriched with a new constant named DEFAULT_THEME. Furthermore, the option for customizing the theme has been added to every method within the class. This allows for tailored visual representation in all the different aspects of our platform, such as buttons, checkboxes, dates, emails, and many more.

• Adaptable Widgets with Theme Support
  Likewise, the PureField class has been upgraded to accept an additional $theme parameter for all of its methods. This enhancement has ensured that all the widgets being called (like Button, Checkbox, DateTime, Email, and more) can now take the theme of choice and accentuate it in their display effectively, thereby creating a unified and visually pleasing user experience.

Benefit:
By propagating the theme configuration throughout the whole platform, we are now able to drive a consistent visual brand identity, which will lead to enhanced usability and stronger brand perception.