feat: Support for Dart 3

[albertodev01]

Why?

• Dependencies need to be updated
• Set minimum SDK constraint to 3
• Add new linter rules

What?

• I have upgraded dependencies in the pubspec.yaml file
• I have improved the documentation

Types of Changes

• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation change (change to update documentation)

Notes

n/a

Checklist

• I have provided a description of the proposed changes.
• I added unit tests for all relevant code.
• I made sure that code coverage is at 100%.
• I added documentation for all relevant code.

[codecov]

Codecov Report

Merging #23 (e994c00) into master (bb94692) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #23   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            9         9           
  Lines          323       320    -3     
=========================================
- Hits           323       320    -3     

Impacted Files	Coverage Δ
lib/src/extensions/fraction_string.dart	100.00% <ø> (ø)
lib/src/extensions/mixed_string.dart	100.00% <ø> (ø)
lib/src/rational.dart	100.00% <ø> (ø)
lib/src/types/egyptian_converter.dart	100.00% <100.00%> (ø)
lib/src/types/mixed.dart	100.00% <100.00%> (ø)
lib/src/types/standard.dart	100.00% <100.00%> (ø)