Add style configurability to Mesop UI

[davorrunje]

Description

Type of change

• New feature (a non-breaking change that adds functionality)

Checklist

• I have conducted a self-review of my own code
• I have made the necessary changes to the documentation
• My changes do not generate any new warnings
• I have added tests to validate the effectiveness of my fix or the functionality of my new feature
• I have included code examples to illustrate the modifications

[codecov]

Codecov Report

Attention: Patch coverage is 63.29588% with 98 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
fastagency/ui/mesop/main.py	26.66%	66 Missing ⚠️
docs/docs_src/tutorial/giphy/simple_main.py	0.00%	16 Missing ⚠️
fastagency/ui/mesop/message.py	82.00%	9 Missing ⚠️
fastagency/ui/mesop/base.py	80.00%	2 Missing and 1 partial ⚠️
fastagency/app.py	88.88%	2 Missing ⚠️
docs/docs_src/getting_started/main_mesop.py	0.00%	1 Missing ⚠️
docs/docs_src/tutorial/giphy/main.py	0.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ
fastagency/base.py	92.79% <ø> (+0.26%)	⬆️
fastagency/logging.py	100.00% <ø> (ø)
fastagency/ui/mesop/components/helpers.py	75.00% <ø> (ø)
fastagency/ui/mesop/components/inputs.py	43.18% <100.00%> (+1.32%)	⬆️
fastagency/ui/mesop/styles.py	100.00% <100.00%> (+100.00%)	⬆️
docs/docs_src/getting_started/main_mesop.py	0.00% <0.00%> (ø)
docs/docs_src/tutorial/giphy/main.py	0.00% <0.00%> (ø)
fastagency/app.py	70.83% <88.88%> (-29.17%)	⬇️
fastagency/ui/mesop/base.py	57.97% <80.00%> (+1.15%)	⬆️
fastagency/ui/mesop/message.py	54.37% <82.00%> (-6.47%)	⬇️
... and 2 more

... and 2 files with indirect coverage changes