add js autodoc default options

[xsjad0]

This allows us to omit the options :members: and private-members on every single autoclass directive.

conf.py

js_autodoc_default_options = {
    "members": True,            # by default False
    "private-members": True,    # by default False
}

JavaScript source

/**
 * TestClass
 */
class TestClass {
    /**
     * A.
     */
    a() {}

    /**
     * B.
     */
    b() {}

    /**
     * C.
     * @private
     */
    c() {}
}

.rst file

.. js:autoclass:: TestClass

html result

Notable changes:

• add config value js_autodoc_default_options (default empty dict)
• implement _default_options() in JSRenderer class
• try to set defaults on initialization of renderer classes (currently only at AutoClassRenderer)
• write some test cases