title: Sphinx-js can't find class documentation
body: <p>I'm trying to setup sphinx_js but I keep receiving this error:</p>
  <pre><code>~/test_sphinx_js$ sphinx-build  -b html docs/source/ docs/build/html/
  Running Sphinx v4.4.0
  building [mo]: targets for 0 po files that are out of date
  building [html]: targets for 1 source files that are out of date
  updating environment: [new config] 1 added, 0 changed, 0 removed
  reading sources... [100%] index                                                                                                                                                                                    
  Sphinx error:
  No documentation was found for object &quot;SomeClass&quot; or any path ending with that.
  </code></pre>
  <p>this is my test project structure:</p>
  <pre><code>.
  ├── docs
  │   ├── build
  │   │   └── html
  │   ├── make.bat
  │   ├── Makefile
  │   └── source
  │       ├── conf.py
  │       ├── index.rst
  │       ├── _static
  │       └── _templates
  └── src
      └── SomeClass.js
  </code></pre>
  <p>and these are the relevant settings and code:</p>
  <p>conf.py</p>
  <pre><code>[...]
  extensions = ['sphinx_js']
  js_source_path = '../../src'
  primary_domain = 'js'
  [...]
  </code></pre>
  <p>index.rst:</p>
  <pre><code>Welcome to SomeDocs's documentation!
  ====================================
  
  .. toctree::
     :maxdepth: 2
     :caption: Contents:
  
  
  
  Indices and tables
  ==================
  
  * :ref:`genindex`
  * :ref:`modindex`
  * :ref:`search`
  
  .. js:autoclass:: SomeClass
  </code></pre>
  <p>SomeClass.js:</p>
  <pre><code>/** Class representing something. */
  export default class SomeClass {
  
      /**
       * Create class.
       * @param {string} name - The name of the object.
       * @param {string} type - The type of object.
       */
      constructor(name, type) {
          this.name = name;
          this.type = type;
  
      }
  }
  </code></pre>
  <p>I must be missing something obvious but I can't wrap my head around it</p>