Add mod documentation in seven languages

docs/en.md

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+# Cthangover: Murakami — a story line of the main game
+
+This mod adds one story line to Cthangover: something prowls the town, and following it leads to a meeting with Murakami. It brings the scenarios of that meeting, Murakami as a character with her portrait and set of expressions, a quest in the journal, and battles. It is part of the Cthangover game and needs the base story (`cthangover_game`) to run.
+
+This page describes how the line is attached to the game and how it starts; what happens later is left for the player.
+
+## How it starts
+
+When Marao comes to the town entrance, a growl comes from the darkness and the player chooses whether to go back home or check the alley:
+
+![The town entrance at night: the text "[A muffled growl came from the darkness]" with the answers Return home and Check the alley.](assets/growl.jpg)
+
+Checking the alley starts the quest **Meeting Murakami**, and its first entry appears in the journal:
+
+![The journal with the active quest Meeting Murakami and its entry "I met a wild wolf in the city; it was trying to get into a locked house."](assets/journal.jpg)
+
+## How it is attached to the base story
+
+The mod changes no file of the base game. It adds scenarios to existing scenes, and the game picks the one to play by its priority and condition:
+
+```scenario
+scene: town_entry
+priority: 10
+condition: MeetingMurakamiQuest.notHasTag("wolf_battle")
+```
+
+- The opening scenario belongs to the scene `town_entry` with priority 10, so it is chosen over the town's ordinary scenarios while its condition holds.
+- Each next step of the line is another scenario of `town_entry` with a higher priority (20, 30) whose condition looks at the tags of the quest `MeetingMurakamiQuest`. The last step plays in the house (`home_vestibule`).
+- Battles start with `battle.init` on the platform's battle system; the outcome is written back as a quest tag, so the next scenario knows what happened.
+- When the line is finished, its conditions no longer hold and the town plays its ordinary scenarios again.
+
+What the mod ships:
+
+- `scenarios/murakami/meeting/` — the four scenarios of the meeting;
+- `quests/quests.json` — the quest with three journal entries;
+- `characters/player/murakami.json` — Murakami as a character, with her picture;
+- `avatars/murakami/` — her expressions for dialogs;
+- the backgrounds of the meeting in `backgrounds/town/meetingmurakami/`;
+- texts in seven languages in `locale/`.
+
+## Turning it off
+
+The line can be left out of the game's collection: the town then plays only its own scenarios, and the quest never appears.
+
+## Known problems
+
+- Two of Marao's expressions used by these scenarios, `marao/what` and `marao/relax`, do not exist in the game, so those lines show no portrait. The Validator reports them as `REF_NOT_FOUND`.