feat: added support for TextCapitalization in DialogTextField

[Katze-942]

This is my first contribution, and I'm still new to Dart. Apologies if the implementation isn't ideal.

I often add images with captions, and having to manually capitalize the first letter every time is tedious. This patch adds automatic capitalization to the text field.

• Code formatting and import sorting has been done with dart format lib/ test/ and dart run import_sorter:main --no-comments
• The commit message uses the format of Conventional Commits
• The commit message describes what has been changed, why it has been changed and how it has been changed
• Every new feature or change of the design/GUI is linked to an approved design proposal in an issue
• Every new feature in the app or the build system has a strategy how this will be tested and maintained from now on for every release, e.g. a volunteer who takes over maintainership

Pull Request has been tested on:

• Android
• iOS
• Browser (Chromium based)
• Browser (Firefox based)
• Browser (WebKit based)
• Desktop Linux
• Desktop Windows
• Desktop macOS

[krille-chan]

LGTM thank you so much :)

[krille-chan]

@Katze-942 Thanks for the contribution. Code looks good to me :-) but the analyzer fails with:

info • Missing a required trailing comma • lib/widgets/adaptive_dialogs/dialog_text_field.dart:36:56 • require_trailing_commas