Update romanize docs and add warning

[wannaphong]

Today, romanize function support a word only by design (rule-base method and deep learning method). It doesn't have preprocessing (word tokenizer and more) like romanization program.

I think we should update romanize docs and add warning if the user give the text that have space to the function.

[bact]

Maybe depends on implementations.

For pythainlp.transliterate.royin.romanize(), it supports the multiwords input, with preprocessing:

pythainlp/pythainlp/transliterate/royin.py

Lines 218 to 219 in aad134d

	words = word_tokenize(text)
	romanized_words = [_romanize(word) for word in words]

[wannaphong]

Maybe depends on implementations.

For pythainlp.transliterate.royin.romanize(), it supports the multiwords input, with preprocessing:

pythainlp/pythainlp/transliterate/royin.py

Lines 218 to 219 in aad134d

	words = word_tokenize(text)
	romanized_words = [_romanize(word) for word in words]

Yes, it depends on the algorithm but it supports just a word by design in the general.