docs: various updates to documentation

- update the unicode quotes to ascii so copy and paste works
- add link to dac2 hd debugging issue
- add link to issue where debugging for dac2 hd occured and was subsequently fixed
- add screenshot and description of alternative dt overlay option

Connects-to: #377
Change-type: patch
Signed-off-by: Aaron Shaw <aaron@balena.io>

docs/05-audio-interfaces.md

@@ -30,7 +30,7 @@ In the balenaCloud dashboard:
 
 Alternatively, you can set this configuration variable in the `Define DT overlays` section under the `Device configuration` menu item:
 
-![DAC Configuration Option 2](https://raw.githubusercontent.com/balenalabs/balena-sound/master/docs/images/dac-vars-2.png)
+![DAC Configuration Option 2](https://raw.githubusercontent.com/balenalabs/balena-sound/master/docs/images/dac-vars-2.png/)
 
 As per the above steps, after adding this power cycling your device will then pull in the new overlay.