Support option of returning best guess or all possible transliterations

[ribose-jeffreylau]

Originally: https://github.com/interscript/lcs/issues/2#issuecomment-578096993

[ronaldtse]

Premise:

• sometimes there are ambiguous conversion rules, such as 1 character converting to 1 out of 2 characters
• in these cases we currently only return the result for the 1st conversion, the 2nd+ rules are ignored

This issue requires implementation of an option to return either a single instance of the conversion result, or all instances of the results.

One can consider that the conversion result space can be:

• a single result (a-b-c) or
• a full set of results (a-{b,d}-c, which is a-b-c and a-d-c).

[webdev778]

Fixed refer to here