feature: help determine os and arch

Signed-off-by: Terry Howe <[email protected]>

versioned_docs/version-1.3.0-beta.1/installation.mdx

@@ -27,6 +27,20 @@ snap install oras --classic
 
 Install ORAS from the latest [release artifacts](https://github.com/oras-project/oras/releases):
 
+In most cases, you can determine operating system and architecture using `uname`:
+
+```bash
+OS="$(uname -s | tr A-Z a-z)"
+ARCH=$(uname -m | sed -e 's/x86_64/amd64/g')
+VERSION="1.2.0"
+curl -LO "https://github.com/oras-project/oras/releases/download/v${VERSION}/oras_${VERSION}_${OS}_${ARCH}.tar.gz"
+mkdir -p oras-install/
+tar -zxf oras_${VERSION}_${OS}_${ARCH}.tar.gz -C oras-install/
+sudo chown root:0 oras-install/oras
+sudo mv oras-install/oras /usr/local/bin/
+rm -rf oras_${VERSION}_${OS}_${ARCH}.tar.gz oras-install/
+```
+
 ### Linux
 
 If you want to install ORAS on an AMD64-based Linux machine, run the following command: