add some initial API code

src/preload.js

@@ -1,2 +1,22 @@
 // See the Electron documentation for details on how to use preload scripts:
 // https://www.electronjs.org/docs/latest/tutorial/process-model#preload-scripts
+
+const { contextBridge, ipcRenderer } = require('electron')
+
+
+// expose an API to choose available devices
+contextBridge.exposeInMainWorld('nanodevices', {
+    list() { ipcRenderer.invoke('nanodevices:list'); },
+    connect(devicename) { ipcRenderer.invoke('nanodevices:connect', devicename); },
+    disconnect() { ipcRenderer.invoke('nanodevices:disconnect'); },
+    on_device_attached(listener) { ipcRenderer.on('nanodevice-attached', (_event, value) => listener(value)); },
+    on_device_detached(listener) { ipcRenderer.on('nanodevice-detached', (_event, value) => listener(value)); },
+});
+
+
+// expose an API to communicate with the nano device
+contextBridge.exposeInMainWorld('nanodevice', {
+    get_value(pid, tid, vid){ ipcRenderer.invoke('nano:get', pid, tid, vid); },
+    set_value(pid, tid, vid, value){ ipcRenderer.invoke('nano:set', pid, tid, vid, value); },
+    on_value(listener){ ipcRenderer.on('nano-onvalue', (_event, value) => listener(value)); }
+});