Lock the stream to the game window's size

Following the browser's resolution left a small applet in the corner of a
large display and made the CPU encoder fall seconds behind.

streaming/streamer/README.md

@@ -24,7 +24,8 @@ FLASHPOINT_HOST_PATH=/path/to/flashpoint docker compose up -d --build
 ```
 
 Open `https://<host>:3001` and accept the self-signed certificate. To play a
-different game, set `GAME_ID` and recreate the container. The launch log is at
+different game, set `GAME_ID`, plus `GAME_WIDTH` and `GAME_HEIGHT` to its
+window size, and recreate the container. The launch log is at
 `/config/fp-launch.log` inside the container.
 
 ## How it works

streaming/streamer/compose.yaml

@@ -11,6 +11,9 @@ services:
       - PUID=${PUID:-1000}
       - PGID=${PGID:-1000}
       - GAME_ID=${GAME_ID:-247a4c93-c252-49c8-8bc9-fb43d5c039df}
+      # Lock the display to the game window's size; the browser scales it to fit
+      - SELKIES_MANUAL_WIDTH=${GAME_WIDTH:-472}
+      - SELKIES_MANUAL_HEIGHT=${GAME_HEIGHT:-400}
       - RESTART_APP=true
       - NO_DECOR=true
       - TITLE=Flashpoint