Hello Sky Tutorial - docs improvements

[hamishwillee]

Bug Page: Writing an Application · PX4 Developer Guide

As discussed in #305 the docs are missing description of CMakeLists.txt and should also include link to final code for comparison.

[anksankita]

My problem is px4_simple_app not listed in Built in apps....please give me the solution

[hamishwillee]

This issue is closed, because the original error (missing make file) was fixed well over a year ago.

@anksankita The guide and was updated well after this error so it is no longer valid. I am therefore closing it. If the app is missing it is most likely because it is not included in the firmware as described in https://dev.px4.io/master/en/apps/hello_sky.html#build-the-applicationfirmware
I would guess that you're targetting FMUv2 where it is not present by default, and you will need to enable it in your custom build.