docs: ADR 0009, feature parity for the other languages

What applies of Japanese's features to Chinese, Korean, Greek, German and
English, with the developer's choices and each decision's reason: Unihan's
characters, KRDict's words and levels, Make Me a Hanzi's and the curator's
own strokes, typed pinyin, radicals and readings by language; what doesn't
apply or has no open data. AGENTS.md, the server's README and the
instance's example environment follow.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

deploy/.env.example

@@ -40,10 +40,12 @@ SOURCE_URL=
 
 # The languages besides Japanese whose dictionaries this instance keeps (the dictionaries
 # service): Chinese from CC-CEDICT, weekly (some 4 MB), in simplified and traditional
-# characters; the rest from Wiktionary (German, Greek and Korean with English meanings,
-# English with German ones), whose whole dump (some 3 GB) it downloads whenever
-# kaikki.org makes a new one, about monthly, and converts in ten minutes. Unset:
-# de,el,en,ko,zh. Empty: none.
+# characters; Korean from KRDict, about monthly (some 84 MB); their characters from
+# Unihan, weekly (some 8 MB); the rest from Wiktionary (German and Greek with English
+# meanings, English with German ones; for Korean the forms of its words and the
+# readings of its Hanja), whose whole dump (some 3 GB) it downloads whenever kaikki.org
+# makes a new one, about monthly, and converts in ten minutes. Unset: de,el,en,ko,zh.
+# Empty: none. Files of a language taken out are removed, and the server unloads them.
 #DICTIONARY_LANGUAGES=de,el,en,ko,zh
 
 # The Jellyfin server the app suggests to this instance's people, who watch and listen