fix(elecraft): the ATU is switch 19, not 20

SWT20 was written from memory of the reference rather than from Table 7,
and 20 is not an ATU switch at all — it would have pressed something else
on a real K3. An operator read the table out for us: switch 19 is the ATU
row, TAP for a tuning cycle and HOLD for tuner in line or bypassed.

Adds the HOLD as its own ATU button, because on the radio they are two
different things: tuning is a cycle you start, bypassing is a state you
leave it in.

Power takes 0-110 W on an Elecraft, per the reference — a K3 makes a
little over its rated output — while a Kenwood keeps 200.

frontend/wailsjs/go/main/App.js

@@ -2434,6 +2434,10 @@ export function TestWebPublishFTP(arg1) {
   return window['go']['main']['App']['TestWebPublishFTP'](arg1);
 }
 
+export function ToggleKenwoodATU() {
+  return window['go']['main']['App']['ToggleKenwoodATU']();
+}
+
 export function TuneKenwoodATU() {
   return window['go']['main']['App']['TuneKenwoodATU']();
 }