Improve documentation of Dimensions module

[ThisIsMissEm]

This includes giving a code sample and noting that window size may be different to screen size on android.

Motivation (required)

Couldn't find any documentation about the difference.

Test Plan (required)

Documentation change; But need to verify it looks right locally.

Next Steps

• CLA is signed.
• Need to check code style: I followed what was in Keyboard.js's documentation comments, but maybe this isn't correct?

[ThisIsMissEm]

Haven't time to verify the changes work locally, but they should — cloning the repo is taking way too long on my internet connection.

[eslint-bot]

no-trailing-spaces: Trailing spaces not allowed.

[eslint-bot]

no-trailing-spaces: Trailing spaces not allowed.

[wcandillon]

I would really like to see this merged 👍

[facebook-github-bot]

@ThisIsMissEm I tried to find reviewers for this pull request and wanted to ping them to take another look. However, based on the blame information for the files in this pull request I couldn't find any reviewers. This sometimes happens when the files in the pull request are new or don't exist on master anymore. Is this pull request still relevant? If yes could you please rebase? In case you know who has context on this code feel free to mention them in a comment (one person is fine). Thanks for reading and hope you will continue contributing to the project.

[ThisIsMissEm]

No idea, it's been 6 months.

…

On 17 Aug 2017, at 7:05 pm, Facebook Community Bot ***@***.***> wrote: @ThisIsMissEm I tried to find reviewers for this pull request and wanted to ping them to take another look. However, based on the blame information for the files in this pull request I couldn't find any reviewers. This sometimes happens when the files in the pull request are new or don't exist on master anymore. Is this pull request still relevant? If yes could you please rebase? In case you know who has context on this code feel free to mention them in a comment (one person is fine). Thanks for reading and hope you will continue contributing to the project. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or mute the thread.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Maybe the issue has been fixed in a recent release, or perhaps it is not affecting a lot of people. If you think this issue should definitely remain open, please let us know why. Thank you for your contributions.

[charpeni]

Thank you for doing this, really useful.

I'll import this into the documentation.

[AlanSl]

@charpeni Did this ever get imported into the documentation? The Dimensions documentation page is still rather sparse on this subject:

NAME   | TYPE           | DESCRIPTION
--     | --             | --
window | DisplayMetrics | Size of the visible Application window.
screen | DisplayMetrics | Size of the device's screen.