[essentials] Find/replace includes to latest format and relative file

[adegeo]

This is going into the working branch. This used a find replace powershell script I wrote to pipe files for processing. This was only processed in the essentials folder, so the replacement relative path is correct.

Find the include references

dir *.md | select-string "include[]" -SimpleMatch | select line -Unique

Line
----
[!include[](~/essentials/includes/get-started.md)]
[!include[](~/essentials/includes/sensor-speed.md)]
[!include[](~/essentials/includes/xamarin-show-essentials.md)]
[!include[](~/essentials/includes/tip-file-result.md)]
[!include[](~/essentials/includes/android-permissions.md)]
[!include[](~/essentials/includes/ios-PresentationSourceBounds.md)]

I then used the docs extension in VSCode to generate the format for the includes (which uses relative pathing):

[!INCLUDE [get-started](includes/get-started.md)]
[!INCLUDE [sensor-speed](includes/sensor-speed.md)]
[!INCLUDE [xamarin-show-essentials](includes/xamarin-show-essentials.md)]
[!INCLUDE [tip-file-result](includes/tip-file-result.md)]
[!INCLUDE [android-permissions](includes/android-permissions.md)]
[!INCLUDE [ios-PresentationSourceBounds](includes/ios-PresentationSourceBounds.md)]

Find/Replace

dir *.md | Replace-TextInFile -Pattern "[!include[](~/essentials/includes/get-started.md)]" -Replacement "[!INCLUDE [get-started](includes/get-started.md)]" -Simple
dir *.md | Replace-TextInFile -Pattern "[!include[](~/essentials/includes/sensor-speed.md)]" -Replacement "[!INCLUDE [sensor-speed](includes/sensor-speed.md)]" -Simple
dir *.md | Replace-TextInFile -Pattern "[!include[](~/essentials/includes/xamarin-show-essentials.md)]" -Replacement "[!INCLUDE [xamarin-show-essentials](includes/xamarin-show-essentials.md)]" -Simple
dir *.md | Replace-TextInFile -Pattern "[!include[](~/essentials/includes/tip-file-result.md)]" -Replacement "[!INCLUDE [tip-file-result](includes/tip-file-result.md)]" -Simple
dir *.md | Replace-TextInFile -Pattern "[!include[](~/essentials/includes/android-permissions.md)]" -Replacement "[!INCLUDE [android-permissions](includes/android-permissions.md)]" -Simple
dir *.md | Replace-TextInFile -Pattern "[!include[](~/essentials/includes/ios-PresentationSourceBounds.md)]" -Replacement "[!INCLUDE [ios-PresentationSourceBounds](includes/ios-PresentationSourceBounds.md)]" -Simple