Custom encoding support

[Olegt0rr]

Description

Added support for custom encoders/decoders

Fixes #1262

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Test A
• Test B

Test Configuration:

• Operating System:
• Python version:

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[github-actions]

✔️ Changelog found.

Thank you for adding a description of the changes

[codecov]

Codecov Report

Merging #1278 (2dc0be6) into dev-3.x (a0ae934) will not change coverage.
Report is 2 commits behind head on dev-3.x.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##           dev-3.x     #1278   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          366       367    +1     
  Lines         9339      9352   +13     
=========================================
+ Hits          9339      9352   +13     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
aiogram/utils/deep_linking.py	100.00% <100.00%> (ø)
aiogram/utils/payload.py	100.00% <100.00%> (ø)