Make a single repository which bundles all examples to reduce release overhead

[gvdongen]

Single repository with general readme.
One directory per example with a dedicated readme.

Tasks

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1. Create restatedev/examples repository documentation#112
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2. Port greeter example to new handlers API #2
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3. Port ticket reservation to new handlers API #4
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4. Try to use npm workspaces for better dependency management #6
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5. Include restatedev/example-shopping-cart-typescript into examples repository #14
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6. Include restatedev/example-food-ordering into examples repository #15
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7. Add simple example for how to integrate Restate with non-Restate handlers #17
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8. Replace existing example repositories with restatedev/examples documentation#123
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9. Change collaborator GHA workflow to add users to restatedev/examples restate#720
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[tillrohrmann]

Done