Fixes displaying single newlines in output markdown and add renderer_options

[ahuang11]

Fixes #5375
Before

After

Primary use case atm:
Langchain outputs newlines as \n so I have to do this:

    def on_llm_new_token(self, token: str, **kwargs) -> None:
        self._entry = self.chat_interface.stream(
            token.replace("\n", "<br>"), self._entry
        )
        return super().on_llm_new_token(token, **kwargs)

[codecov]

Codecov Report

Merging #5376 (a7694e8) into main (47c4a05) will decrease coverage by 10.08%.
Report is 3 commits behind head on main.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##             main    #5376       +/-   ##
===========================================
- Coverage   82.77%   72.70%   -10.08%     
===========================================
  Files         274      274               
  Lines       39861    39879       +18     
===========================================
- Hits        32996    28995     -4001     
- Misses       6865    10884     +4019     

Flag	Coverage Δ
ui-tests	?
unitexamples-tests	72.70% <100.00%> (+<0.01%)	⬆️

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Files Changed	Coverage Δ
panel/pane/markup.py	89.78% <100.00%> (+0.13%)	⬆️
panel/tests/pane/test_markup.py	99.42% <100.00%> (+0.04%)	⬆️
panel/widgets/base.py	92.52% <100.00%> (+0.07%)	⬆️

... and 59 files with indirect coverage changes

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[philippjfr]

Looks good, but could you please also update the docs in the reference notebook?

[ahuang11]

Added

[philippjfr]

Thank you!