`vim.lsp.util.apply_text_edits` needs `offset-encoding`

[Omochice]

summary

Add a missing needed argument. Fix #20.

background

After https://github.com/neovim/neovim/commit/bc722c8a74766e14aff3a8e2fc46db72ed864053, offset-encoding became a needed argument.

By the way, I found undefined argument and fix it too on c3005208bff55b42923944cdf5f2806ec1e5e35e.