This issue will track the technical implementation of a new version of Sandcastle for CesiumJS. Design and features will primarily be worked out and discussed elsewhere. If you want to provide feedback on features you'd like to see please add them to our post on the community forum

High level plan

We plan to create a new workspace/package within our mono-repo to keep the new Sandcastle project separated but co-located with CesiumJS.

• itwin-ui: We expect to use the newest version of iTwin/Bentley UI library for both components and styling as much as possible. We may contribute improvements or components back to it as necessary.
• React: This is a given if we want to make use of iTwinUI.
• Monaco: We'll want to balance robust feature set with usability for users who prefer a more minimal code editing experience. This should greatly increase the DX of the editor bringing familiarity for any already used to using VSCode
• TypeScript: Unless there is a reason not to. This will be isolated to it's own package so it's separate from the rest of CesiumJS
• Build tools: We'll likely get started with the Vite plugin for react, and if needed we can use esbuild like the CesiumJS library itself

As we build out the new version we plan to have a beta/dev deployment for people to test against. More info on this as build systems and CI get set up

CC @ggetz