Convert EuiCopy component to TypeScript

[scottybollinger]

Summary

Convert EuiCopy component to TypeScript.

Checklist

• This was checked in mobile
• This was checked in IE11
• This was checked in dark mode
• Any props added have proper autodocs
• Documentation examples were added
• A changelog entry exists and is marked appropriately
• This was checked for breaking changes and labeled appropriately
• Jest tests were updated or added to match the most common scenarios
• This was checked against keyboard-only and screenreader scenarios
• This required updates to Framer X components

[cchaos]

Thanks @scottybollinger !

As mentioned in Slack, we are in the process of actually converting the components to true TS instead of adding the TS defs as a shim. We can absolutely proceed with reviewing this PR as is unless you want to take a stab at converting to TS?

[scottybollinger]

@cchaos I went ahead and converted it and updated the title and description of the PR. Let me know if you need anything else!

[chandlerprall]

this prop is optional, please update the interface to match: beforeMessage?: ReactNode;

[scottybollinger]

Thanks @chandlerprall. Just to be sure, is there an associated defaultProps value for this as well?

[chandlerprall]

No, there is not (thanks for double checking!) - it's allowed to be null and in that case nothing is rendered.

[cchaos]

Thanks, LGTM!

[chandlerprall]

Changes LGTM