vscode: add support for VSCodium (#9080)

Co-authored-by: Babak K. Shandiz <babak.k.shandiz@gmail.com>
Co-authored-by: Marc Cornellà <marc.cornella@live.com>

plugins/vscode/vscode.plugin.zsh

@@ -1,17 +1,28 @@
-# VScode zsh plugin
+# VS Code (stable / insiders) / VSCodium zsh plugin
 # Authors:
 #   https://github.com/MarsiBarsi (original author)
 #   https://github.com/babakks
+#   https://github.com/SteelShot
 
-# Use the stable VS Code release, unless the Insiders version is the only
-# available installation
-if ! which code > /dev/null && which code-insiders > /dev/null; then
-  : ${VSCODE:=code-insiders}
-else
-  : ${VSCODE:=code}
+# Verify if any manual user choice of VS Code exists first.
+if [[ -n "$VSCODE" ]] && ! which $VSCODE &>/dev/null; then
+  echo "'$VSCODE' flavour of VS Code not detected."
+  unset VSCODE
+fi
+
+# Otherwise, try to detect a flavour of VS Code.
+if [[ -z "$VSCODE" ]]; then
+  if which code &>/dev/null; then
+    VSCODE=code
+  elif which code-insiders &>/dev/null; then
+    VSCODE=code-insiders
+  elif which codium &>/dev/null; then
+    VSCODE=codium
+  else
+    return
+  fi
 fi
 
-# Define aliases
 alias vsc="$VSCODE ."
 alias vsca="$VSCODE --add"
 alias vscd="$VSCODE --diff"