Add Library.resolve to README.

Author: mbostock

README.md

@@ -881,7 +881,7 @@ Semiotic = r("semiotic")
 
 The Observable standard library is built-in to Observable, so you don’t normally need to install or instantiate it directly. If you use NPM, `npm install @observablehq/stdlib`.
 
-<a href="#Library" name="Library">#</a> <b>Library</b>([<i>resolve</i>]) [<>](https://github.com/observablehq/stdlib/blob/master/src/index.js "Source")
+<a href="#Library" name="Library">#</a> <b>Library</b>([<i>resolve</i>]) [<>](https://github.com/observablehq/stdlib/blob/master/src/library.js "Source")
 
 Returns a new standard library object. If a *resolve* function is specified, it is a function that returns a promise to the URL of the module with the specified *name*; this is used internally by [require](#require) (and by extension, [md](#md) and [tex](#tex)). See [d3-require](https://github.com/d3/d3-require/blob/master/README.md) for details.
 
@@ -893,3 +893,7 @@ const canvas = library.DOM.canvas(960, 500);
 ```
 
 The properties on the returned *library* instance correspond to the symbols (documented above) that are available in Observable notebooks. However, note that the library fields (such as *library*.now) are *definitions*, not values: the values may be wrapped in a function which, when invoked, returns the corresponding value.
+
+<a href="#Library_resolve" name="Library_resolve">#</a> Library.<b>resolve</b>(<i>name</i>, [<i>base</i>]) [<>](https://github.com/observablehq/stdlib/blob/master/src/library.js "Source")
+
+An alias for [d3.require.resolve](https://github.com/d3/d3-require/blob/master/README.md#require_resolve).