fix(tauri.js) `tauri icon` with `--icon` flag, closes #750 (#774)

.changes/tauri-icon.md

@@ -0,0 +1,5 @@
+---
+"tauri.js": patch
+---
+
+Fixes the `tauri icon` usage with the `--icon` flag. Previously, only the `-i` flag worked.

cli/tauri.js/bin/tauri-icon.js

@@ -21,7 +21,7 @@ const argv = parseArgs(process.argv.slice(2), {
     h: 'help',
     l: 'log',
     c: 'config',
-    s: 'source',
+    i: 'icon',
     t: 'target'
   },
   boolean: ['h', 'l']