Game version in the menu: VERSION holds vYYYYMM-NNNNN, shown on the title screen and in the pause menu, tools/bump_version.py raises it with every change

INSTALL.md

@@ -116,6 +116,16 @@ A forgotten password is set again on the server with `docker compose stop saves
 
 All requests except health and login need `Authorization: Bearer <token>`. Limits: 1 MB per savegame, 500 MB in total, 30 write requests and 20 login attempts per minute. Settings: `SAVE_DIR` (default `/data`), `LISTEN` (default `0.0.0.0:8080`).
 
+## Version
+
+`VERSION` holds the game version as `vYYYYMM-NNNNN`: year and month of the change, then the number of
+changes in that month (`v202611-00001`). The title screen and the pause menu show it, `src/menu.rs`
+reads the file with `include_str!`, and a test checks the scheme.
+
+**With every change to the game** run `python3 tools/bump_version.py` before committing: it raises the
+number by one (a new month starts again at `00001`) and prints the old and the new version. Do not edit
+`VERSION` by hand.
+
 ## Adding a language
 
 1. Copy `lang/en.lang` to `lang/<code>.lang` and translate the texts (placeholders `{0}`, `{1}` stay as they are).
@@ -129,3 +139,4 @@ All requests except health and login need `Authorization: Bearer <token>`. Limit
 | `play/DungeonCraft.html` | build the WASM file, then `python3 tools/make_standalone.py <www dir with dungeoncraft.wasm and mq_js_bundle.js> play/DungeonCraft.html` (the Docker image builds the same file under `/standalone/`) |
 | `docs/img/units`, `docs/img/icons` | `cargo test --release export_doc_images -- --ignored` |
 | `BESTIARY.md` | `python3 tools/make_bestiary.py` |
+| `VERSION` | `python3 tools/bump_version.py` - with every change to the game |