README.md: Update according to ESP32 port

README.md

@@ -112,7 +112,7 @@ building `enet`.
 A stripped version of the executable, as well as game assets, will be
 located in `build/cdimg`.
 
-#### Dependencies
+##### Dependencies
 
 A cross-compiled `i386-mingw32` version of all required dependencies
 is needed before building `jancity`.
@@ -126,6 +126,32 @@ of this writing, so it is provisionally provided on
 Read [the documentation](doc/BUILD-win9x.md) for further reference on
 how to build the dependencies from source.
 
+#### Espressif ESP32
+
+```sh
+. $IDF_PATH/export.sh
+ENETDIR=<enet-prefix> \
+    cmake -B build -DCMAKE_TOOLCHAIN_FILE=cmake/win9x-toolchain.cmake
+cmake --build build
+```
+
+Where:
+
+- `ENETDIR` is the path to the cross-compiled version for `enet`.
+
+##### Dependencies
+
+[`esp-idf`](https://github.com/espressif/esp-idf) is required to build this
+or any ESP32-related project. The `release/v5.1` branch is assumed here.
+As pointed out by
+[their documentation](https://docs.espressif.com/projects/esp-idf/en/v5.1.2/esp32/api-guides/build-system.html?highlight=idf_path#initialization),
+remember to assign the `IDF_PATH` environment variable to the directory
+where `esp-idf` is located.
+
+`esp-idf` requires to build `enet` using a custom CMake wrapper on top of it.
+For this project, this has been provided by the
+[`enet-esp32`](https://gitea.privatedns.org/xavi/enet-esp32) repository.
+
 ## License
 
 Unless stated otherwise, **jancity** follows the license described by the