Update to React18

[pkerpedjiev]

Description

What was changed in this pull request?

• Update React to react 18
• Change hglib.viewer() function to return a promise rather than an object. This is necessary because the React component render isn't necessarily synchronous and we may not have a reference to it immediately. We'll likely have to bump the major version number of the library.

Still have to:

• Add an upgrade guide to the docs

Why is it necessary?

• Getting with the times.

Fixes #___

Checklist

• Set proper GitHub labels (e.g. v1.6+, ignore if you don't know)
• Unit tests added or updated
• Documentation added or updated
• Example(s) added or updated
• Update schema.json if there are changes to the viewconf JSON structure format
• Screenshot for visual changes (e.g. new tracks or UI changes)
• Updated CHANGELOG.md

[sehilyi]

Hi @pkerpedjiev, just checking in since I am excited about this PR. Do you plan to upgrade React version in the near future? I assume, due to the recent adoption of Vite, this will need to be revisited.

[pkerpedjiev]

Yeah this PR will need to be rebased on the latest vite changes. I haven't had time to work on it recently but it's something we'll have to do at some point.