update docker tag information (#785)

DOCKER_README.md

@@ -1,17 +1,43 @@
 # Docker
 
+## Important note
+Starting with v0.18.0, tag names have changed. You may no longer use `latest`, `master`, `vX.X.X`.
+
 ## Build your own containers
 This image provides a method for you to easily use the latest Sunshine release in your own docker projects. It is not
 intended to use as a standalone container at this point, and should be considered experimental.
 
 ```dockerfile
-FROM  lizardbyte/sunshine
+ARG SUNSHINE_VERSION=latest
+ARG SUNSHINE_OS=ubuntu-22.04
+FROM lizardbyte/sunshine:${SUNSHINE_VERSION}-${SUNSHINE_OS}
 
 # install Steam, Wayland, etc.
 
 ENTRYPOINT steam && sunshine
 ```
 
+### SUNSHINE_VERSION
+- `latest`, `master`, `vX.X.X`
+- `nightly`
+- commit hash
+
+### SUNSHINE_OS
+Sunshine images are available, based on the following base images.
+
+- `debian-bullseye`
+- `fedora-36`
+- `fedora-37`
+- `ubuntu-20.04`
+- `ubuntu-22.04`
+
+### Tags
+You must combine the `SUNSHINE_VERSION` and `SUNSHINE_OS` to determine the tag to pull. The format should be
+`<SUNSHINE_VERSION>-<SUNSHINE_OS>`. For example, `latest-ubuntu-22.04`.
+
+See all our available tags on [docker hub](https://hub.docker.com/r/lizardbyte/sunshine/tags) or
+[ghcr](https://github.com/LizardByte/Sunshine/pkgs/container/sunshine/versions) for more info.
+
 ## Where used
 This is a list of docker projects using Sunshine. Something missing? Let us know about it!
 
@@ -97,12 +123,12 @@ If you want to change the PUID or PGID after the image has been built, it will r
 
 ## Supported Architectures
 
-Specifying `lizardbyte/sunshine:latest` or `ghcr.io/lizardbyte/sunshine:latest` should retrieve the correct
-image for your architecture.
+Specifying `lizardbyte/sunshine:latest-<SUNSHINE_OS>` or `ghcr.io/lizardbyte/sunshine:latest-<SUNSHINE_OS>` should
+retrieve the correct image for your architecture.
 
-The architectures supported by this image are:
+The architectures supported by these images are:
 
-| Architecture | Available |
-|:------------:|:---------:|
-|    x86-64    |     ✅     |
-|    arm64     |     ✅     |
+|  Architecture   | Available |
+|:---------------:|:---------:|
+| amd64 / x86_64  |     ✅     |
+| arm64 / aarch64 |     ✅     |