fix: log Extension.name, not the object itself

electron-devtools-installer v3's installExtension resolved to a
string name; v4 resolves to an Electron Extension object. The
success log was string-interpolating the object, producing
"Installed dev extension: [object Object]". The install itself was
working; only the log message was wrong. Read `.name` off the
returned Extension instead.

Author: cwillisf

src/main/index.js

@@ -431,7 +431,9 @@ app.on('ready', () => {
                 // WARNING: depending on a lot of things including the version of Electron `installExtension` might
                 // return a promise that never resolves, especially if the extension is already installed.
                 installExtension(extension).then(
-                    extensionName => log(`Installed dev extension: ${extensionName}`),
+                    // v3 resolved with a string name; v4 resolves with an Electron
+                    // Extension object. Read `.name` rather than relying on toString.
+                    installed => log(`Installed dev extension: ${installed.name}`),
                     errorMessage => log.error(`Error installing dev extension: ${errorMessage}`)
                 );
             }