Finish up docker docs and fix docker non-buildx builds

Dockerfile

@@ -1,3 +1,6 @@
+ARG TARGETPLATFORM=linux/amd64
+ARG BUILDPLATFORM=${TARGETPLATFORM}
+
 FROM --platform=${BUILDPLATFORM} mcr.microsoft.com/dotnet/sdk:6.0 AS builder
 
 ARG TARGETPLATFORM
@@ -9,7 +12,8 @@ COPY . ./
 # Build and package release based on target architecture
 RUN dotnet build -v m
 WORKDIR /TShock/TShockLauncher
-RUN case "${TARGETPLATFORM}" in \
+RUN \ 
+  case "${TARGETPLATFORM}" in \
     "linux/amd64") export ARCH="linux-x64" \
     ;; \
     "linux/arm64") export ARCH="linux-arm64" \

docs/docker.md

@@ -1,12 +1,45 @@
 # Docker Setup
 
-## Build Image:
-`docker build -t tshock .`
-## and run:
+In order to run TShock in a docker container, you would need to have mountpoints for
+ - `/tshock` (TShock config files, logs and crash reports)
+ - `/worlds`
+ - `/plugins`
+ - `/server` (optional, if you want to mount TShock's cwd)
+
+These folders can be mounted using `-v <host_folder>:<container>`
+
+Open ports can also be passed through using `-p <host_port>:<container_port>`.
+ - `7777` for Terraria
+ - `7878` for TShock's REST API
+
+For Example:
 ```bash
+# Building the image
+docker build -t tshock:linux-x64 --build-arg TARGETPLATFORM=linux-x64 .
+
+# Running the image
 docker run -p 7777:7777 -p 7878:7878 \
-           -v <save path>:/tshock \
-           -v <world path>:/worlds \
-           -v <plugin path>:/plugins \
-           --rm -it tshock [-world /worlds/<world file>] <other cmdline flags>
+           -v /home/cider/tshock/:/tshock \
+           -v /home/cider/.local/share/Terraria/Worlds:/worlds \
+           -v /home/cider/tshock/plugins:/plugins \
+           --rm -it tshock:linux-x64 \
+           -world /worlds/backflip.wld -motd "OMFG DOCKER"
+```
+
+## Building for Other Platforms
+
+Using `docker buildx`, you could build [multi-platform images](https://docs.docker.com/build/building/multi-platform/) for TShock.
+
+For Example:
+```bash
+# Building the image using buildx and loading it into docker
+sudo docker buildx build -t tshock:linux-arm64 --platform linux/arm64 --load .
+
+# Running the image
+docker run -p 7777:7777 -p 7878:7878 \
+           -v /home/cider/tshock/:/tshock \
+           -v /home/cider/.local/share/Terraria/Worlds:/worlds \
+           -v /home/cider/tshock/plugins:/plugins \
+           --rm -it tshock:linux-arm64 \
+           -world /worlds/backflip.wld -motd "ARM64 ftw"
 ```