Example: Update the existing example_plugin and add C++ example plugin

plugins/example_plugin_cpp/README.md

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+# Example plugin
+
+This is just a simple example plugin which can be used as a template.
+The plugin logs the FSOpenFile calls via UDP (**Only when build via `make DEBUG=1`**).
+
+The logging can be enabled/disabled via the WUPS Config menu (press L, DPAD Down and Minus on the GamePad, Pro Controller or Classic Controller).
+
+## Installation
+
+(`[ENVIRONMENT]` is a placeholder for the actual environment name.)
+
+1. Copy the file `ExamplePlugin.wps` into `sd:/wiiu/environments/[ENVIRONMENT]/plugins`.
+2. Requires the [WiiUPluginLoaderBackend](https://github.com/wiiu-env/WiiUPluginLoaderBackend) in `sd:/wiiu/environments/[ENVIRONMENT]/modules`.
+
+Start the environment (e.g Aroma) and the backend should load the plugin.
+
+## Building
+
+For building you need:
+
+- [wups](https://github.com/Maschell/WiiUPluginSystem)
+- [wut](https://github.com/devkitpro/wut)
+
+Install them (in this order) according to their README's. Don't forget the dependencies of the libs itself.
+
+Then you should be able to compile via `make` (with no logging) or `make DEBUG=1` (with logging).
+
+## Buildflags
+
+### Logging
+
+Building via `make` only logs errors (via OSReport). To enable logging via the [LoggingModule](https://github.com/wiiu-env/LoggingModule) set `DEBUG` to `1` or `VERBOSE`.
+
+`make` Logs errors only (via OSReport).  
+`make DEBUG=1` Enables information and error logging via [LoggingModule](https://github.com/wiiu-env/LoggingModule).  
+`make DEBUG=VERBOSE` Enables verbose information and error logging via [LoggingModule](https://github.com/wiiu-env/LoggingModule).
+
+If the [LoggingModule](https://github.com/wiiu-env/LoggingModule) is not present, it'll fallback to UDP (Port 4405) and [CafeOS](https://github.com/wiiu-env/USBSerialLoggingModule) logging.
+
+## Building using the Dockerfile
+
+It's possible to use a docker image for building. This way you don't need anything installed on your host system.
+
+```
+# Build docker image (only needed once)
+docker build . -t example-plugin-builder
+
+# make 
+docker run -it --rm -v ${PWD}:/project example-plugin-builder make DEBUG=1
+
+# make clean
+docker run -it --rm -v ${PWD}:/project example-plugin-builder make clean
+```
+
+## Format the code via docker
+
+`docker run --rm -v ${PWD}:/src ghcr.io/wiiu-env/clang-format:13.0.0-2 -r ./src -i`