(GH-184) Display info when add-in is pre-release & fix preprocessor directive

[augustoproiete]

• Display information alert when the add-in is a pre-release version
• Include the &prerelease parameter in the preprocessor directive example

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Closes #184

[pascalberger]

@augustoproiete Is there a reason why you have Allow Edits by maintainers disabled?

I tried to bring this branch up to date but got a permission error.

[augustoproiete]

@pascalberger It's a missing feature of GitHub for me... I keep all my forks in a separate organization to remove the noise on my GitHub user account, and GitHub doesn't allow me to set "Allow Edits by maintainers" because of that unfortunately.

Anyway, I rebased the branch just now against latest master

[pascalberger]

@augustoproiete your changes have been merged, thanks for your contribution 👍

[augustoproiete]

@pascalberger It's a missing feature of GitHub for me... I keep all my forks in a separate organization to remove the noise on my GitHub user account, and GitHub doesn't allow me to set "Allow Edits by maintainers" because of that unfortunately.

@pascalberger I gave your user permission to write to my forks (website & cake) - I'm hoping this will resolve the "Allow Edits by maintainers" in future PRs once you've accepted the invite.