Set minimum dimensions for debugger-shell windows (facebook#56081)

Summary:
Pull Request resolved: facebook#56081

Changelog: [Internal]

Reviewed By: vzaidman

Differential Revision: D96391528

fbshipit-source-id: 45057e8113cec08a422e2be93d02cad5a4318345

Author: huntie

packages/debugger-shell/src/electron/MainInstanceEntryPoint.js

@@ -62,6 +62,8 @@ function handleLaunchArgs(argv: string[]) {
         width: 1200,
         height: 600,
       }),
+      minWidth: 400,
+      minHeight: 300,
       webPreferences: {
         partition: 'persist:react-native-devtools',
         preload: require.resolve('./preload.js'),