Fix word aggregation with many whitespaces

[fl4p]

Exclude whitespace chars or chars with a small bbox from word aggregation.

Thes whitespace here collapse the table structure:

datasheets/littelfuse/IXFP110N15T2.pdf

[fl4p]

using this interpreter class helps:

class PDFPageInterpreter_NOWS(PDFPageInterpreter):
    def render_contents(
        self,
        resources: Dict[object, object],
        streams: Sequence[object],
        ctm: Matrix = MATRIX_IDENTITY,
    ) -> None:
        r = super().render_contents(resources, streams, ctm)
        for obj in list(self.device.cur_item):
            if isinstance(obj, LTChar):
                c = obj.get_text()
                if c.isspace():
                    self.device.cur_item._objs.remove(obj)
        return r