Pycantonese

Added
- Added the `parse_text` for analyzing Cantonese text data.
- Characters-to-Jyutping conversion:
The `characters_to_jyutping` function now has the `segmenter` kwarg for
customizing word segmentation.
- Added support for Python 3.10.
- Turned on Windows testing on CircleCI.
- Added `pyproject.toml`. Related to preferring `setup.cfg` for specifying
build metadata and options.

Changed
- Characters-to-Jyutping conversion:
For the `characters_to_jyutping` function,
in case rime-cantonese and HKCanCor don't agree,
rime-cantonese data (more accurate) is preferred.
- Updated the rime-cantonese data to the latest `2021.05.16` release,
improving both characters-to-Jyutping conversion and word segmentation.
- Updated the PyLangAcq dependency to v0.16.0, allowing PyCantonese's `CHATReader`
to use the new methods `to_chat`, `to_strs`, `info`, `head`, and `tail`.
- Switched to `setup.cfg` to fully specify build metadata and options,
while keeping a minimal `setup.py` for backward compatibility.
Related to the new `pyproject.toml`.

Removed
- Dropped support for Python 3.6.

Security
- Turned on `safety` and `bandit` checks at CircleCI builds.

Fixed
- Allowed PyLangAcq v0.14.* for real.

Changed
- Allowed PyLangAcq v0.14.*, thereby adding the new features of the `filter` method to `CHATReader`
and optional parallelization for CHAT data processing.

Fixed
- Fixed the `search` method of `CHATReader` when `by_tokens` is `False`.

Fixed
- Fixed the previously inoperational methods `append`, `append_left`, `extend`, and `extend_left`
of the class `CHATReader` through the upstream PyLangAcq package.
- Retrained the part-of-speech tagger, after the minor character fix from v3.2.3.
- Raised `NotImplementedError` for the method `ipsyn` of `CHATReader`,
since the upstream method works only for English.

Fixed
* Fixed character issues in the built-in HKCanCor data: 𥄫

Fixed
* Fixed a CHAT parsing issue when correction and repetition are combined,
by bumping the pylangacq dependency from v0.13.0 to v0.13.1.