Add VitePress

[anishkny]

No description provided.

[anishkny]

@zachleat @huguestennier and other mods, not sure why builds are failing - doesn't seem related to my change. e.g. PR #817 also seems to be failing with same syndrome:

4:09:02 PM: error Error: Request failed with status code 401
4:09:02 PM:     at createError (/opt/build/repo/node_modules/axios/lib/core/createError.js:16:15)
4:09:02 PM:     at settle (/opt/build/repo/node_modules/axios/lib/core/settle.js:17:12)
4:09:02 PM:     at IncomingMessage.handleStreamEnd (/opt/build/repo/node_modules/axios/lib/adapters/http.js:236:11)
4:09:02 PM:     at IncomingMessage.emit (events.js:327:22)
4:09:02 PM:     at endReadableNT (_stream_readable.js:1221:12)
4:09:02 PM:     at processTicksAndRejections (internal/process/task_queues.js:84:21) {
4:09:02 PM:   config: {
4:09:02 PM:     url: 'https://api.github.com/gists',
4:09:02 PM:     method: 'get',
4:09:02 PM:     params: {},
...

[huguestennier]

@anishkny Yes, we have a problem where we do deploy preview without sensitives variables but our current code currently expect these API keys to work properly. I filed an issue here: #819 we'll be looking into it.