Prepare For v3 (fleaflet#1355)

* Removed useless `subdomains` properties from examples
Updated CHANGELOG
Improved pubspec.yaml

* Added new maintainer

* Added improved support for Flutter 3.3.0

* Set minimum Flutter constraint to 3.3.0
Ignored FVM (@JaffaKetchup's machine)

Prepared For v2.2.0 Release (fleaflet#1324)

* Prepared for v2.2.0 release

* Update CHANGELOG

Fixed Null-Safety Errors (fleaflet#1318)

* Fixed null-safety errors
Updated package version

* Updated CHANGELOG

* Fixed bug

'User-Agent' Header Generation & More (fleaflet#1294)

* Added `userAgentPackageName` implementation
Improved headers implementation
Deprecated `NonCachingNetworkTileProvider` in favour of `NetworkNoRetryTileProvider`
Updated example pages with changes
Improved documentation

* Temporarily fixed multiple User-Agent headers
Fixed usage of `NetworkTileProvider`
Fixed deprecation notice invalid symbol reference

* Removed some old TODOs
Simplified `_positionedForOverlay` (solved TODO)
Improved maintainability
Improved documentation

* Removed old deprecations (`placeholderImage` and `attributionBuilder`)

* Atempt to fix `HttpOverrides` issue - unsuccessful: dart-lang/sdk#49382 (comment)

* Fixed issues
Added custom `ImageProvider`s
Reduced reliance on 'universal_io' library
Prepared for review

* Fixed web platform support
Seperated tile_provider.dart for web and other plaforms
Removed 'universal_io' dependency
Updated CHANGELOG

* Fixed 'Refused to set unsafe header' error

* Improved in-code documentation

* Removed deprecated API remenant `attributionAlignment` from `TileLayerOptions`

* Fix false positive linter warning: see https://github.com/dart-lang/linter/issues/1381

* Improved documentation
Refactored base `TileProvider` into independent file

Prepare For New Documentation (fleaflet#1286)

* Prepare for new documentation website

* Fixed broken link in issue template selector
Added documentation field to pubspec

* Update Example README

* Added Correct Date To CHANGELOG
Added Credits To CHANGELOG