Detects and replaces protocol-style links (e.g., http://, https://, ftp://) in a given sentence
with unique placeholders like __URL1__, __URL2__, etc. This is useful for preparing text for
translation or further processing while preserving original URLs.
replace_urls_with_placeholders(sentence)A list with two elements:
The input sentence with URLs replaced by placeholders.
A character vector of the extracted URLs.
A character string potentially containing one or more URLs.