feat: update Marlin start message parsing (#683)

* Updated Marlin start message parsing

Some flavors of Marlin print 'echo:start' on serial connect instead of plain 'start'.
The controller will not finish its connection sequence and seem unresponsive

* Fix regex to make echo: optional

Co-authored-by: ejt4x <ejt@LAPTOP-J94AOG0A.localdomain>
Co-authored-by: Cheton Wu <cheton@gmail.com>

src/server/controllers/Marlin/MarlinLineParserResultStart.js

@@ -1,7 +1,7 @@
 class MarlinLineParserResultStart {
     // start
     static parse(line) {
-        const r = line.match(/^start$/);
+        const r = line.match(/^(?:echo:)?start$/);
         if (!r) {
             return null;
         }