<!-- Enter a brief description/summary of your PR here. What does it fix/what does it change/how was it tested (even manually, if necessary)? -->
## Summary of the Pull Request
Add a new action that can contain multiple other actions.
<!-- Other than the issue solved, is this relevant to any other issues/existing PRs? -->
## References
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## PR Checklist
* [x] Closes#3992
* [x] CLA signed. If not, go over [here](https://cla.opensource.microsoft.com/microsoft/Terminal) and sign the CLA
* [ ] Tests added/passed
* [ ] Documentation updated. If checked, please file a pull request on [our docs repo](https://github.com/MicrosoftDocs/terminal) and link it here: #xxx
* [x] Schema updated.
* [ ] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx
<!-- Provide a more detailed description of the PR, other things fixed or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments
Creates a shortcut action that allows a list of actions to be specified as arguments. Steals a bunch of the serialization code from my other pr. Overall, because I had the serialization code written already, this was remarkably easy.
I can't think of any combined action to be added to the defaults, so I think this is just a thing for the documentation unless someone else has a good example. I know there are lot of times when the recommended workaround is "make an action with commandline wt.exe ..." and this could be a good replacement for that, but that is all personalized.
I didn't add this to the command line parsing, since the command line is already a way to run multiple actions.
<!-- Describe how you validated the behavior. Add automated tests wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed
Created a new command, confirmed that "Move right->down" showed up in the command palette, and that running it did the correct behavior (moving right one pane, then down one pane).
```
{
"command": {
"action": "multipleActions",
"name": "Move right->down",
"actions": [
{"action": "moveFocus", "direction": "right" },
{"action": "moveFocus", "direction": "down" },
]
}
}
```
8d81497eb7