fix: folium.folium.Map._to_png()의 Firefox path related errors

fix: folium.folium.Map._to_png()의 Firefox path related errors

[Problem]
When the `folium.folium.Map._to_png()` method is used in an environment where the Firefox web browser is not installed, the following error is output.

[Example]
```
WebDriverException: Message: 'geckodriver' executable needs to be in PATH.
```

[Solution]

Added a Boolean argument called `chrome` to the `folium.folium.Map._to_png()` method. If this value is `False`, Firefox webdriver is used as before, and if this value is `True`, Chrome webdriver is used. Additionally, we used the `webdriver_manager` package, which automatically installs chromedriver considering the version of the Chrome web browser installed on the client.

[Test]

- Legacy error-generating logic

```python
import io
import folium
from PIL import Image

m = folium.Map(location = [37.53, 127.054],
               zoom_start = 14)

img_data = m._to_png(5)
img = Image.open(io.BytesIO(img_data))
```

- Logic applied to the solution

```python
import io
import folium
from PIL import Image

m = folium.Map(location = [37.53, 127.054],
               zoom_start = 14)

img_data = m._to_png(delay=5,
                     chrome=True)
img = Image.open(io.BytesIO(img_data))
```

Author: WooilJeong

folium/folium.py

@@ -297,7 +297,7 @@ def _repr_html_(self, **kwargs):
             out = self._parent._repr_html_(**kwargs)
         return out
 
-    def _to_png(self, delay=3):
+    def _to_png(self, delay=3, chrome=False):
         """Export the HTML to byte representation of a PNG image.
 
         Uses selenium to render the HTML and record a PNG. You may need to
@@ -311,11 +311,15 @@ def _to_png(self, delay=3):
         """
         if self._png_image is None:
             from selenium import webdriver
-
-            options = webdriver.firefox.options.Options()
-            options.add_argument('--headless')
-            driver = webdriver.Firefox(options=options)
-
+            if chrome is True:
+                from webdriver_manager.chrome import ChromeDriverManager
+                options = webdriver.ChromeOptions()
+                options.add_argument('--headless')
+                driver = webdriver.Chrome(ChromeDriverManager().install(), options=options)
+            else:
+                options = webdriver.firefox.options.Options()
+                options.add_argument('--headless')
+                driver = webdriver.Firefox(options=options)
             html = self.get_root().render()
             with temp_html_filepath(html) as fname:
                 # We need the tempfile to avoid JS security issues.

requirements-dev.txt

@@ -30,6 +30,7 @@ setuptools_scm
 selenium
 sphinx
 twine>=3.2.0
+webdriver-manager
 wheel
 vega_datasets
 vincent