Add Waveterm Icon to Linux (#120)

* add icon for Linux

The app icon previously did not show up in Linux. This change fixes that
by providing the wave-logo-dark.png to the electron Browser Window.

* set the icon to only use the direct path on linux

The previous change was only required on linux and not on mac. This
ensures the old behavior will continue to be done on mac while using the
new behavior on linux.

src/electron/emain.ts

@@ -250,6 +250,7 @@ function createMainWindow(clientData) {
         minWidth: 800,
         minHeight: 600,
         transparent: true,
+        icon: (unamePlatform == "linux") ? "public/logos/wave-logo-dark.png" : undefined,
         webPreferences: {
             preload: path.join(getAppBasePath(), DistDir, "preload.js"),
         },