Broken bracketting when mfenced is not used

[MoMaT]

When _use_fence is set to False* the open bracket is not generated correctly. The added mo is treated like mfenced and is made a parent rather than a sister of the subsequent elements.

asciimathml/asciitomathml/asciitomathml.py

Line 644 in 3bf2a2d

self._append_el = element

A fix looks like this:

def _handle_open_fence(self, token):
    if self._use_fence:
        element = self._make_element('mfenced', open=token, separators='', close="")
        self._append_el.append(element)
        self._append_el = element
    else:
        element = self._make_element('mo', text=token)
        self._append_el.append(element)

*) mfenced is deprecated, and Firefox > 73 has dropped support for it
https://developer.mozilla.org/en-US/docs/Web/MathML/Element/mfenced

[paulhtremblay]

OK. It has been so long since I looked at this code, so I will have to trust you. :) Do you want to make a branch and apply the patch?