add screenshot and update readme

apps.json

@@ -2641,6 +2641,7 @@
     "name": "Navigation Compass",
     "version": "0.05",
     "description": "Compass with linear display as for GPSNAV. Has Tilt compensation and remembers calibration.",
+    "screenshots": [{"url":"screenshot_b2.png"}],
     "icon": "magnav.png",
     "tags": "tool,outdoors",
     "supports": ["BANGLEJS","BANGLEJS2"],

apps/magnav/README.md

@@ -13,10 +13,13 @@ Note: Charging your Bangle due to the magnetic connector clamp seems to require
 ## Controls
 
 *BTN1* - marks the current heading with a blue circle - see screen shot. This can be used to take a bearing and then follow it..
+(Swipe UP on Bangle 2)
 
 *BTN2* - invokes calibration ( can be cancelled if pressed accidentally).
+(*BTN1* on Bangle 2)
 
 *BTN3* - cancels the marker (blue circle not displayed)
+(swipe DOWN on Bangle 2)
 
 
 ## Support

apps/magnav/magnav_b1.js

@@ -1,5 +1,5 @@
 const Yoff = 80;
-var pal2color = new Uint16Array([0x0000,0xffff,0x07ff,0xC618],0,2);
+var pal2color = new Uint16Array([g.theme.bg,g.theme.fg,g.theme.fg2,0xC618],0,2);
 var buf = Graphics.createArrayBuffer(240,60,2,{msb:true});
 Bangle.setLCDTimeout(30);