Update Firmware flashing page (betaflight#418)

* Update Firmware flashing page

* notes for FrSkyOSD and Flash Storage, Custom Defines listing added

* implement review suggestions

* make image in night mode

* update image

* fixes from review comments

* Restore FrSky OSD

* update and include a user-level defines list

* remove commented out defines with better grep

* minor fixes

* update defines list to exclude those from mk

* updated the defines list, added notes about displaying the log and build options

* update link to defines listing in cloud-build-api

* Update docs/development/Defines.md

Co-authored-by: nerdCopter <56646290+nerdCopter@users.noreply.github.com>

---------

Co-authored-by: Mark Haslinghuis <mark@numloq.nl>
Co-authored-by: nerdCopter <56646290+nerdCopter@users.noreply.github.com>

docs/development/API/Cloud-Build-API.md

@@ -15,8 +15,8 @@ Uses config repo for targets using defines only. For more information see [How t
 
 ## Usage
 
-For optimal use please select ONLY the appropiate hardware for the flight controller after selecting the right target (using auto-detect button).
-Choices below are further described in the [wiki/Firmware Flasher page](/docs/wiki/configurator/firmware-flasher-tab)
+For optimal use please select ONLY the appropiate hardware for the flight controller after selecting the correct target (using auto-detect button).
+The options below are further described in the [wiki/Firmware Flasher page](/docs/wiki/configurator/firmware-flasher-tab). We also have a complete listing of [build options](/docs/development/Defines).
 
 ### Radio Protocols