The main differences between the Idris 1 and Idris 2 versions is in the
parser. Idris 1 version uses lightyear for parsing, while the Idris 2
version uses the Data.String.Parser from contrib.

PR #13 is what does the upgrade, so you can see the changes there.

Check the README for which features were implemented at this point, but
for a TLDR, all the basic types and literals are in, and couple of
builtins but not much.