Corpus not loading in Pyodide

[taviowong]

Describe the bug
Pyodide is a tool for running Python packages in the browser. In its current state, pycantonese cannot be run in Pyodide due to the use of multi-threading during data loading of corpus.

To reproduce

1. Go to the online REPL at https://pyodide.org/en/stable/console.html
2. Run the following script

>>> import micropip
>>> await micropip.install('setuptools')
>>> await micropip.install('pycantonese')
>>> import pycantonese
>>> pycantonese.segment('但願人長久，千裡共嬋娟')

3. An error is thrown: "RuntimeError: can't start new thread". Full stack trace as follows.

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/lib/python3.12/site-packages/pycantonese/parsing.py", line 170, in parse_text
    _get_utterance(sent, segment_kwargs, pos_tag_kwargs, participant)
  File "/lib/python3.12/site-packages/pycantonese/parsing.py", line 56, in _get_utterance
    words, tags, jps = _parse_text(unparsed_sent, segment_kwargs, pos_tag_kwargs)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/lib/python3.12/site-packages/pycantonese/parsing.py", line 27, in _parse_text
    chars_jps = characters_to_jyutping(text, **(segment_kwargs or {}))
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/lib/python3.12/site-packages/pycantonese/jyutping/characters.py", line 101, in characters_to_jyutping
    words_to_jyutping, chars_to_jyutping = _get_words_characters_to_jyutping()
                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/lib/python3.12/site-packages/pycantonese/jyutping/characters.py", line 14, in _get_words_characters_to_jyutping
    corpus = hkcancor()
             ^^^^^^^^^^
  File "/lib/python3.12/site-packages/pycantonese/corpus.py", line 396, in hkcancor
    reader = _HKCanCorReader.from_dir(data_dir)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/lib/python3.12/site-packages/pylangacq/chat.py", line 187, in wrapper
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/lib/python3.12/site-packages/pylangacq/chat.py", line 1057, in from_dir
    return cls.from_files(
           ^^^^^^^^^^^^^^^
  File "/lib/python3.12/site-packages/pylangacq/chat.py", line 187, in wrapper
    return func(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/lib/python3.12/site-packages/pylangacq/chat.py", line 1005, in from_files
    strs = list(executor.map(_open_file, paths))
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/lib/python312.zip/concurrent/futures/_base.py", line 608, in map
    fs = [self.submit(fn, *args) for args in zip(*iterables)]
          ^^^^^^^^^^^^^^^^^^^^^^
  File "/lib/python312.zip/concurrent/futures/thread.py", line 179, in submit
    self._adjust_thread_count()
  File "/lib/python312.zip/concurrent/futures/thread.py", line 202, in _adjust_thread_count
    t.start()
  File "/lib/python312.zip/threading.py", line 992, in start
    _start_new_thread(self._bootstrap, ())
RuntimeError: can't start new thread

Expected behavior
The sentence can be segmented without error:
['但願', '人', '長久', '，', '千', '裡', '共', '嬋娟']

System (please complete the following information):

• Operating System: N/A
• PyCantonese version: 3.4.0

Additional context

• Pyodide does not support multi-threading (source: https://pyodide.org/en/stable/usage/wasm-constraints.html#included-but-not-working-modules).
• Allowing pycantonese to be run in JavaScript/browser will open up to many different opportunities (e.g. Cantonese-themed web apps, browser extensions).
• The _HKCanCorReader.from_dir() function supports disabling multi-threading using parallel=False. Preliminary testing shows that pycantonese works in Pyodide with multi-threading disabled.
• Can you add an environment variable for overriding the argument so that pycantonese can be loaded properly?