dev(narugo): allow use string as exporter (equals to SaveExporter('xx…

[narugo1992]

from ditk import logging

from waifuc.action import FileExtAction, ModeConvertAction
from waifuc.source import ZerochanSource

logging.try_init_root(level=logging.INFO)

ZerochanSource('Texas', select='full', strict=True).attach(
    ModeConvertAction(),
    FileExtAction('.jpg'),
)[:10].export('test_q')

# equals to `SaveExporter('test_q', no_meta=True)`

[codecov[bot]]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (9b3ef25) 57.96% compared to head (c2dcfa2) 57.89%. Report is 2 commits behind head on main.

Files	Patch %	Lines
waifuc/source/base.py	40.00%	3 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #35 +/- ## ========================================== - Coverage 57.96% 57.89% -0.08% ========================================== Files 47 47 Lines 2353 2356 +3 ========================================== Hits 1364 1364 - Misses 989 992 +3 ``` | [Flag](https://app.codecov.io/gh/deepghs/waifuc/pull/35/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=deepghs) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/deepghs/waifuc/pull/35/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=deepghs) | `57.89% <40.00%> (-0.08%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=deepghs#carryforward-flags-in-the-pull-request-comment) to find out more.

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