[CN-3075] GHA to push to GHCR

[tovar-rodrigo]

We prefer small, well tested pull requests.

Please refer to Contributing to Spinnaker.

When filling out a pull request, please consider the following:

• Follow the commit message conventions found here.
• Provide a descriptive summary for your changes.
• If it fixes a bug or resolves a feature request, be sure to link to that issue.
• Add inline code comments to changes that might not be obvious.
• Squash your commits as you keep adding changes.
• Add a comment to @spinnaker/reviewers for review if your issue has been outstanding for more than 3 days.

Note that we are unlikely to accept pull requests that add features without prior discussion. The best way to propose a feature is to open an issue first and discuss your ideas there before implementing them.

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Helpful Tips

Add screenshots and annotations

• In OSX Mojave, you can capture screenshots and add annotations. https://support.apple.com/en-us/HT201361
• Another app you can use is https://www.getcloudapp.com/.

Add a gif to show an action

GIFs are great to show an action, however they sometimes move too fast.
One way to improve them is to capture 3 pieces of content:

• screenshot before an action
• screenshot after the action
• gif of the action
• You can edit a gif using https://ezgif.com/

Put a border around a screenshot/gif

Add a border to help improve the readability.

<kbd>![](https://www.spinnaker.io/assets/images/spinnaker-logo-inline.svg)</kbd>

Add expandable sections

Add expandable sections to hide away large code blocks/images or reduce the motion of a gifs

const example = 'spinnaker spinnaker SPINNAKER';