embedded api

[mbostock]

TODO:

• [x] Generate embed script (e.g., /chart.js) during preview
• [x] Generate embed script (e.g., /chart.js) during build via embedPaths dynamicPaths
• [x] Fix build so that module rendering applies content-hashed aliases (via resolvers)
• [x] Fix build so that assets & imports of embedded modules are included
• [x] Fix build so that the tree output is relevant for embedded modules
• [x] Fix messy types in build
• [x] Embed script script takes precedence over page (e.g., /chart.js.md)
• [x] Ignore pre-empted pages (/chart.js.md given /chart.js) in the sidebar & pager
• [x] Compute transitive static imports for preloading
• [x] Inline file registration to avoid ordering problem
• [x] Allow CORS during preview
• [x] Restrict CORS preview to specific origins
• [x] Documentation
• [x] Tests

Fixes #1084. Fixes #1583.

[mbostock]

Would be simpler to just invert the precedence and have /chart.js.md take precedence over /chart.js? I don’t think it matters which one we choose; we just have to pick one, so we should pick whatever’s easier for us. Edit: There is a philosophical reason to give /chart.js precedence which is that it is an exact match and more specific than /chart.js.md, and hence we should stay the course. Further edit: I think we could just disallow /chart.js.md entirely and require that pages only have a single extension. That restriction should simplify things and feels reasonable and more forward-looking.

[mbostock]

Boo, one of our tests has a page sub/page1..10.md which already violates the double extension rule, suggesting that we should allow pages to have double extensions but fix the precedence issue… I need to think more.