Add 'Bundle Patcher Architecture'

Bundle-Patcher-Architecture.md

@@ -0,0 +1,25 @@
+This is an (likely incomplete) documentation of how dtmm's process to deploy mods and patch game bundles works and what data it writes.
+
+## settings.ini
+
+The game's `application_settings/settings-common.ini` is changed with
+
+```diff
+-boot_script = "scripts/main"
++boot_script = "scripts/mod_main"
+```
+
+This allows us to run our own entry point before the game's code, without touching the actual `scripts/main` file.
+
+## packages/boot
+
+Several files are added to `packages/boot`:
+
+* `scripts/mod_main.lua`: The very first file of code that the game will run at startup. This sets up mod handling and then calls Fatshark's actual `scripts/main` entry point.
+* `scripts/mods/mod_data.lua`: This file mod metadata and the load order, all of which the mod manager will use to load the installed mods.
+* `scripts/mods/manager.lua`: An adapted version of `ModManager` from VT2 that handles loading and initialization of mods.
+* `packages/mods.package`: The `.package` file that points to the separate mod collection bundle
+
+## packages/mods
+
+This bundle serves as the root package from which all mod packages can be reached. Collecting them here avoids bloating `packages/boot` too much.