Publish internal libraries to npm

[mbostock]

There are a handful of libraries that are currently internally defined, but we should publish them to npm so that they don’t need to be treated specially. These are:

• npm:@observablehq/runtime observablehq:runtime
• npm:@observablehq/stdlib observablehq:stdlib
• npm:@observablehq/dot
• npm:@observablehq/duckdb
• npm:@observablehq/inputs
• npm:@observablehq/mermaid
• npm:@observablehq/tex
• npm:@observablehq/sqlite
• npm:@observablehq/xlsx observablehq:stdlib/xlsx
• npm:@observablehq/zip observablehq:stdlib/zip