adding kannada language support (miniproject3)

[nishantsubramani]

• What kind of change does this PR introduce? (Language addition, bug fix, feature, docs update, ...)

This PR introduces the addition of Kannada (kan-Knda) to epitran. It has preprocess, map, postprocess, and tests.

• Checklist

• Have you added adequate tests on epitran/test?
• Have you updated the language list in README.md?

• Sources of information for the test samples (I'm a native speaker, books, online resources, ...)

Online resources, textbooks, and consultation from a Kannada speaker. Some familiarity with similar languages such as Malayalam and Tamil. Below are the list of the resources used:

• Schiffman, Harold. "A Reference Grammar of Spoken Kannada." (1979).
• Zydenbos, Robert J. "A manual of Modern Kannada." (2020).
• https://en.wikipedia.org/wiki/Kannada_script
• https://en.wikibooks.org/wiki/Kannada
• https://en.wikipedia.org/wiki/Kannada#Phonology
• https://www.omniglot.com/writing/kannada.htm
• https://www.omniglot.com/language/numbers/kannada.htm

• Sources of information for the rules (I'm a native speaker, books, online resources, ...)

Same online resources, textbooks, and consultation from a Kannada speaker. Familiarity with similar languages (Malayalam and Tamil). See cites above.

• What is the current behavior? (You can also link to an open issue here)
  N/A

• What is the new behavior (if this is a feature change)?
  N/A

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  N/A

[dmort27]

Code looks fine.