fix: skip installing packages when nothing to install (#6)

this changeset is to fix the issues related to installing packages.

- treat packages as string instead of array of strings
https://containers.dev/implementors/features/#options-property
- replace commas (`,`) to spaces (` `)

Author: kosperera

src/deno/install.sh

@@ -61,8 +61,10 @@ EXE="${BIN_DIR}/deno"
 
 # Install global packages if specified
 # See https://docs.deno.com/runtime/reference/cli/install/#global-installation
-if [ "${#PACKAGES[@]}" -gt 0 ]; then
+if [ -n "${PACKAGES}" ]; then
     echo "Installing global packages..."
+    # Replace commas to spaces.
+    PACKAGES=${PACKAGES//,/ }
     su "${_REMOTE_USER}" -c "$EXE install --global --allow-net --allow-read ${PACKAGES}"
 fi