improvement: rename `env_at_cursor` to `current_env` #75

Job	Run time
ash-ci / mix deps.get	16s
ash-ci / MIX_ENV=dev mix.compile	21s
ash-ci / audit	34s
ash-ci / MIX_ENV=test mix.compile	26s
ash-ci / mix docs	23s
ash-ci / mix credo --strict	4s
ash-ci / mix format --check-formatted	22s
ash-ci / mix dialyzer	2m 12s
ash-ci / mix sobelow	24s
ash-ci / mix spark.cheat_sheets --check	3s
ash-ci / mix spark.formatter --check	3s
ash-ci / mix test	49s
ash-ci / mix deps.unlock --check-unused	20s
ash-ci / Deploy docs to GitHub pages.	7s
ash-ci / Release	0s
	6m 24s

Provide feedback