Add emscripten build instructions

emscripten/README.md

@@ -1,3 +1,80 @@
-# EasyRPG buildscripts
+# Emscripten buildscript
+
+This repository provides build files to easily compile the libraries used by
+the EasyRPG project for emscripten (web).
+
+## Requirements
+
+Only Linux and macOS are supported. On Windows, consider using WSL2 (install
+Ubuntu through the Windows Store).
+
+## In this repository
+
+To build `liblcf` as part of the buildscripts, set the environment variable
+`BUILD_LIBLCF` to `1`:
+
+```
+export BUILD_LIBLCF=1
+```
+
+Run `0_build_everything.sh` to obtain all the necessary dependencies:
+
+```
+./0_build_everything.sh
+```
+
+Building will take a while.
+
+## In the Player repository
+
+### Configuring
+
+**Option 1**: In `builds/cmake/CMakePresetsUser.json`, set
+`EASYRPG_BUILDSCRIPTS` to the path of the buildscripts repository.
+
+**Option 2**: Set the environment variable `EASYRPG_BUILDSCRIPTS` to the path
+of the buildscripts repository:
+
+```
+export EASYRPG_BUILDSCRIPTS=/path/to/buildscripts
+```
+
+To configure the Player, run:
+
+```
+cmake --preset emscripten-[BUILD_TYPE]
+```
+
+Options for ``[BUILD_TYPE]``:
+
+- `debug`: Debug build
+- `relwithdebinfo`: Release build with debug symbols
+- `release`: Release build without debug symbols (recommended)
+
+Other useful options:
+
+- `-DPLAYER_BUILD_LIBLCF=ON`: Builds `liblcf` if you haven't compiled it as
+part of the buildscripts
+- `-DPLAYER_JS_OUTPUT_NAME=index`: By default, the resulting file is called
+`easyrpg-player.html`. This option names it `index.html`.
+
+### Building
+
+To build the Player run:
+
+```
+cmake --build --preset=[PRESET]
+```
+
+`[PRESET]` should match the value used after `--preset` in the configure step.
+
+The resulting HTML, JS, and WASM files will be located in `build/[PRESET]`.
+
+Copy them to their own directory and place any games inside a `games/` subdirectory.
+
+### Deployment
+
+For further information, read our [web player set up guide].
+
+[web player set up guide]: https://easyrpg.org/player/guide/webplayer/
 
-## Emscripten specifics