docs(import-bundle): Update bundle source formats, including endoScript

packages/import-bundle/README.md

@@ -18,13 +18,19 @@ Each call to `importBundle` creates a new `Compartment`. The globals of the new
 
 ## Module Formats
 
-The source can be bundled in a variety of "formats". By default, `bundleSource` uses a format named `getExports`, in which the source tree is linearized into a single CommonJS-style string, and wrapped in a callable function that provides the `exports` and `module.exports` context to which the exports can be attached. `importBundle` recognizes this format, and invokes the function thus defined, to return the namespace object.
+The source can be bundled in a variety of "formats".
 
-A more sophisticated format is named `nestedEvaluate`. In this mode, the source tree is converted into a table of evaluable strings, one for each original module. This table is then encoded and wrapped as before. The evaluation process uses a separate evaluator call for each module, providing an opportunity to attach a distinct `sourceMap` to each one. This preserves relative filenames in subsequent debugging information and stack traces.
+By default, `bundleSource` uses a format named `endoZipBase64`, in which the source modules and a "compartment map" are captured in a Zip file and base-64 encoded. The compartment map describes how to construct a set of [Hardened JavaScript](https://hardenedjs.org) compartments and how to load and link the source modules between them.
+
+The `endoScript` format captures the sources as a single JavaScript program that completes with the entry module's namespace object.
+
+The `getExport` format captures the sources as a single CommonJS-style string, and wrapped in a callable function that provides the `exports` and `module.exports` context to which the exports can be attached.
+
+More sophisticated than `getExport` is named `nestedEvaluate`. In this mode, the source tree is converted into a table of evaluable strings, one for each original module. This table is then encoded and wrapped as before. The evaluation process uses a separate evaluator call for each module, providing an opportunity to attach a distinct `sourceMap` to each one. This preserves relative filenames in subsequent debugging information and stack traces.
 
 To set a base prefix for these relative filenames, provide the `filePrefix` option.
 
-Note that the `nestedEvaluate` format requires an endowment named `require`, although it will only be called if the source tree imported one of the few modules on the `bundle-source` "external" list.
+Note that the `nestedEvaluate` format receives a global endowment named `require`, although it will only be called if the source tree imported one of the few modules on the `bundle-source` "external" list.
 
 ## Options