export_as_rtf: support non-monospaced characters like Chinese

[chengcheng-ma]

Currently, export_as_rtf() only supports the Courier font for table cells. As a result:
Non-monospaced fonts (e.g., Chinese, Arial, Times New Roman) cannot be used;
Tables with wide characters (e.g., Chinese) become misaligned.

If there are any plans or possibilities to extend export_as_rtf() to support additional fonts, so that tables with non-monospaced text can be properly aligned.

[Melkiades]

rtf is not fully supported or actively developed by us. JnJ uses it fully. You can find their implementation as junco::tt_to_tlgrtf