feat!: (BREAKING) v2.1.0, attempt to fix waa edge-case, upgrade dependencies

[jeroen-meijer]

Description

This PR does the following:

• Fix シークヮーサー and シマウヮー conversion edge-cases (thanks to @Moseco and @HighLiuk)
• Change minimum required Dart version to 3.0.0.
• Add FVM config.
• Add CSpell spell checking config.
• Remove package:equatable dependency.
• Upgrade dependencies.
• Upgrade all dev dependencies and linter.

Related issues and PRs

Closes #18
Closes #19
Closes #22
Closes #23

[jeroen-meijer]

@Moseco I've implemented the Hepburn change, but it works differently thank you might expect.

In katakana, シークヮーサー correctly becomes shiikuwaasaa.
In hiragana, しーくゎーさー becomes shi-kuwa-sa-, which is also correct and conforms to how the library converts the ー when used in hiragana.

From the docs from the KanaKit.toRomaji function:

Converts all kana characters of the [input] to romaji.

The [input] String cannot be null. If an empty String is provided, an empty String will be returned immediately.

If this [config]'s [KanaKitConfig.upcaseKatakana] is true, katakana characters will be converted to uppercase characters. ignored.

// With KanaKitConfig.upcaseKatakana == false (default)
toRomaji('ひらがな　カタカナ'); // "hiragana katakana"
toRomaji('げーむ　ゲーム'); // "ge-mu geemu"
// With KanaKitConfig.upcaseKatakana == true
toRomaji('ひらがな　カタカナ'); // "hiragana KATAKANA"
toRomaji('げーむ　ゲーム'); // "ge-mu GEEMU"

[Moseco]

@jeroen-meijer Cool, thanks for implementing the changes!

One other thing. Since I originally made the PR to fix the rare kana issue I also added support for converting ー found in katakana to a hyphen - when using toRomagi. Previously it would just throw an error if ー did not follow a supported vowel. It looks that is included in this branch too. If you want to keep that we can add it to the changelog and make a test for it. The only word I have ever seen with it is パンピアンーミンドリン/Pumpian-Mindlin from enamdict (proper noun dictionary).

[jeroen-meijer]

@Moseco Got it, thanks. I think that might describe a different edge-case, right?

I'll go ahead and merge this for now and do a release to unblock other projects. If this pops up as an issue, you or someone else can make a ticket for it.