Fix legacy build

The build process failed because webpack does not allow failed imports
when it is run as a module.
This detects modules with default exports and only generates import
statements for default exports where they are available.

config/jsdoc/plugins/default-export.cjs

@@ -0,0 +1,35 @@
+const defaultExports = {};
+const path = require('path');
+const moduleRoot = path.join(process.cwd(), 'src');
+
+// Tag default exported Identifiers because their name should be the same as the module name.
+exports.astNodeVisitor = {
+  visitNode: function (node, e, parser, currentSourceName) {
+    if (node.parent && node.parent.type === 'ExportDefaultDeclaration') {
+      const modulePath = path
+        .relative(moduleRoot, currentSourceName)
+        .replace(/\.js$/, '');
+      const exportName =
+        'module:' +
+        modulePath.replace(/\\/g, '/') +
+        (node.name ? '~' + node.name : '');
+      defaultExports[exportName] = true;
+    }
+  },
+};
+
+exports.handlers = {
+  processingComplete(e) {
+    const byLongname = e.doclets.index.longname;
+    for (const name in defaultExports) {
+      if (!(name in byLongname)) {
+        throw new Error(
+          `missing ${name} in doclet index, did you forget a @module tag?`
+        );
+      }
+      byLongname[name].forEach(function (doclet) {
+        doclet.isDefaultExport = true;
+      });
+    }
+  },
+};