Fix Viewer API definitions and include in CI

The Viewer API definitions do not compile because of missing imports and
anonymous objects are typed as `Object`. These issues were not caught
during CI because the test project was not compiling anything from the
Viewer API.

As an example of the first problem:

```
/**
 * @implements MyInterface
 */
export class MyClass {
    ...
}
```

will generate a broken definition that doesn’t import MyInterface:

```
/**
 * @implements MyInterface
 */
export class MyClass implements MyInterface {
    ...
}
```

This can be fixed by adding a typedef jsdoc to specify the import:

```
/** @typedef {import("./otherFile").MyInterface} MyInterface */
```

See https://github.com/jsdoc/jsdoc/issues/1537 and
https://github.com/microsoft/TypeScript/issues/22160 for more details.

As an example of the second problem:

```
/**
 * Gets the size of the specified page, converted from PDF units to inches.
 * @param {Object} An Object containing the properties: {Array} `view`,
 *   {number} `userUnit`, and {number} `rotate`.
 */
function getPageSizeInches({ view, userUnit, rotate }) {
    ...
}
```

generates the broken definition:

```
function getPageSizeInches({ view, userUnit, rotate }: Object) {
    ...
}
```

The jsdoc should specify the type of each nested property:

```
/**
 * Gets the size of the specified page, converted from PDF units to inches.
 * @param {Object} options An object containing the properties: {Array} `view`,
 *   {number} `userUnit`, and {number} `rotate`.
 * @param {number[]} options.view
 * @param {number} options.userUnit
 * @param {number} options.rotate
 */
```

web/struct_tree_layer_builder.js

@@ -13,6 +13,9 @@
  * limitations under the License.
  */
 
+// eslint-disable-next-line max-len
+/** @typedef {import("./interfaces").IPDFStructTreeLayerFactory} IPDFStructTreeLayerFactory */
+
 const PDF_ROLE_TO_HTML_ROLE = {
   // Document level structure types
   Document: null, // There's a "document" role, but it doesn't make sense here.