Extended Katakana

[vedxyz]

https://en.wikipedia.org/wiki/Katakana#Extended_katakana

Support for some of the extended katakana might be a nice addition to free mode.
Not really urgent however, since it's probably better/enough to pick up a few of these naturally as you come across them.

[maitodesu]

@vedxyz working on this one brother, will share here and open a MR.

[maitodesu]

🎌 Extended katakana is now up in #20

Opened a PR for this → #20

✨ What it adds

40 extended katakana as a fourth board in Free Practice, sitting below Katakana Combinations:

ヴァ va	ヴィ vi	ヴ vu	ヴェ ve	ヴォ vo
ファ fa	フィ fi		フェ fe	フォ fo
ツァ tsa	ツィ tsi		ツェ tse	ツォ tso
クァ kwa	クィ kwi		クェ kwe	クォ kwo
グァ gwa
	ウィ wi		ウェ we	ウォ wo
	ティ ti	トゥ tu
	ディ di	ドゥ du
	スィ si		シェ she
	ズィ zi		ジェ je
			チェ che
			イェ ye
テュ tyu	デュ dyu	フュ fyu	ヴュ vyu
キェ kye	ギェ gye	ニェ nye	ヒェ hye	ミェ mye

Columns are aligned on a/i/u/e/o just like the main board, which is why some cells are empty.

🔰 Beginner-safe by default

You said it's "probably better/enough to pick up a few of these naturally" — so nothing is forced on anyone:

• 🔕 Every row defaults to off
• 🔗 The board carries a dimmed caption linking straight to the Wikipedia section, so it's obvious these sit outside the standard syllabary
• 🎯 Free Practice only — Brute Force is untouched, so the from-scratch curriculum still ends at "You have learnt katakana" without a 40-kana loanword detour

🧹 What's deliberately left out

The full Wikipedia table is ~101 entries. The other ~61 are excluded on purpose — bidakuon (カ゚), rare-l (ラ゚) and three-kana forms (ウィェ) are built on the combining mark U+309A, which renders as a dotted-circle box in many fonts, and they're phonetic notation rather than loanword katakana. Obsolete ヷヸヹヺ are out too. Each is a one-liner to add back if you'd rather have them.

🔊 One known gap

Play Sound is silent on these — the audio host has no files for the extended romaji (fa, vu, ti, she, je, che all 404, while ka/kya/fu return 200). It fails quietly, no crash. Filling that in needs a second audio source, so it belongs in its own change.

🐛 Unrelated bug spotted along the way

While checking whether the other practice modes needed this, I found that Word Practice has wrong answers today, independent of this PR. wanakana 5.1.0 romanizes extended katakana character-by-character, so three words already in the shipped list expect the wrong romaji:

Word	Expects	Should be
ファイル	fuairu	fairu
アイディア	aideia	aidia
ボランティア	boranteia	borantia

Not touched in the PR — happy to open a separate issue for it if useful. 🙂

This also covers the ヴ / vu part of #8.