Add basic type stubs (#221) (#215)

* feat: add basic type stubs

* feat: add types for constants

* feat: add type for `MarkdownConverter` class

* ci: add basic job for checking types

* feat: add new constant

* ci: install types as required

* ci: install types package manually

* test: add strict coverage for types

* fix: allow `strip_document` to be `None`

* feat: expand types for MarkdownConverter

* fix: do not use `Unpack` as it requires Python 3.12

* feat: define `MarkdownConverter#convert_soup`

* feat: improve type for `code_language_callback`

* chore: add end-of-file newline

* refactor: use `Union` for now

tests/types.py

@@ -0,0 +1,70 @@
+from markdownify import markdownify, ASTERISK, BACKSLASH, LSTRIP, RSTRIP, SPACES, STRIP, UNDERLINED, UNDERSCORE, MarkdownConverter
+from bs4 import BeautifulSoup
+from typing import Union
+
+markdownify("<p>Hello</p>") == "Hello"  # test default of STRIP
+markdownify("<p>Hello</p>", strip_document=LSTRIP) == "Hello\n\n"
+markdownify("<p>Hello</p>", strip_document=RSTRIP) == "\n\nHello"
+markdownify("<p>Hello</p>", strip_document=STRIP) == "Hello"
+markdownify("<p>Hello</p>", strip_document=None) == "\n\nHello\n\n"
+
+# default options
+MarkdownConverter(
+    autolinks=True,
+    bs4_options='html.parser',
+    bullets='*+-',
+    code_language='',
+    code_language_callback=None,
+    convert=None,
+    default_title=False,
+    escape_asterisks=True,
+    escape_underscores=True,
+    escape_misc=False,
+    heading_style=UNDERLINED,
+    keep_inline_images_in=[],
+    newline_style=SPACES,
+    strip=None,
+    strip_document=STRIP,
+    strip_pre=STRIP,
+    strong_em_symbol=ASTERISK,
+    sub_symbol='',
+    sup_symbol='',
+    table_infer_header=False,
+    wrap=False,
+    wrap_width=80,
+).convert("")
+
+# custom options
+MarkdownConverter(
+    strip_document=None,
+    bullets="-",
+    escape_asterisks=True,
+    escape_underscores=True,
+    escape_misc=True,
+    autolinks=True,
+    default_title=True,
+    newline_style=BACKSLASH,
+    sup_symbol='^',
+    sub_symbol='^',
+    keep_inline_images_in=['h3'],
+    wrap=True,
+    wrap_width=80,
+    strong_em_symbol=UNDERSCORE,
+    code_language='python',
+    code_language_callback=None
+).convert("")
+
+html = '<b>test</b>'
+soup = BeautifulSoup(html, 'html.parser')
+MarkdownConverter().convert_soup(soup) == '**test**'
+
+
+def callback(el: BeautifulSoup) -> Union[str, None]:
+    return el['class'][0] if el.has_attr('class') else None
+
+
+MarkdownConverter(code_language_callback=callback).convert("")
+MarkdownConverter(code_language_callback=lambda el: None).convert("")
+
+markdownify('<pre class="python">test\n    foo\nbar</pre>', code_language_callback=callback)
+markdownify('<pre class="python">test\n    foo\nbar</pre>', code_language_callback=lambda el: None)