Add a script to build DSL dictionaries

[oxij]

The dictionaries in https://github.com/open-dsl-dict/ipa-dict-dsl are 7 years old.

This adds build.py script that generates DSL files for all the data available files in the repository (in two encodings, because some software wants them in UTF16). It could be easily modified to build other release stuff (like JSONs) too, but I don't need other stuff, so.

With this applied, I would suggest either regenerating the data in https://github.com/open-dsl-dict/ipa-dict-dsl or just archiving that repository and distributing DSL files via Releases here.