Update docs with single file

docs/source/userguide-zh.rst

@@ -5,6 +5,7 @@
 
 -  ``radiobee`` 目前仅支持中英、英中对齐。
 -  ``radiobee`` 目前仅支持纯文本文件上载 (txt, md, csv 等)。 以后可能会支持 ``docx``, ``pdf``, ``srt``, ``html`` 等格式。
+-  ``file 2`` 为空白时，``radiobee`` 则会视 ``file 1`` 为中英文混合文本及试着分离中英文，然后进行对齐。
 -  第二次上载文件前请点击"Clear"。
 -  ``tf_type`` ``idf_type`` ``dl_type`` ``norm``: 一般无需理会这些参数。
 -  ``esp`` 和 ``min_samples`` 的建议值 -- ``esp`` (最小 ``epsilon``): 8-12, ``min_samples``: 4-8.

docs/source/userguide.rst

@@ -4,6 +4,8 @@ How to use
 -   ``radiobee aligner`` is a sibling of `bumblebee aligner`. To know more about these aligners, please join qq group `316287378`.
 
 -   Uploaded files should be in pure text format (txt, md, csv etc). ``docx``, ``pdf``, ``srt``, ``html`` etc may be supported later on.
+- If ``file 2`` is left blank, ``radibee`` will treat ``file 1`` as mixed English-Chinese text and attempt to separate English and Chinese texts before procedding to align them.
+
 -   Click "Clear" first for subsequent submits when uploading files.
 -  ``tf_type`` ``idf_type`` ``dl_type`` ``norm``: Normally there is no need to touch these unless you know what you are doing.
 -   Suggested ``esp`` and ``min_samples`` values -- ``esp`` (minimum epsilon): 8-12, ``min_samples``: 4-8.