As it turns out, in GitHub API paginated requests, page numbering is
1-based. (https://developer.github.com/v3/#pagination)
Starting at page 0 (which returns the first page), results in making the
same request twice and logging incorrect numbers (since the first 100
items are listed twice).
PR Close#25671
Previously, Travis pushed the build artitfacts to the preview server.
This required us to use JWT to secure the POST request from Travis, to
ensure we couldn't receive malicious builds.
JWT has been deprecated and we are moving our builds to CircleCI.
This commit rewrites the TypeScript part of the preview server that
handles converting build artifact into hosted previews of the docs.