Merge branch 'add_env_file' into 'master'

add env file to fix rta env in conda

See merge request !14

environment.yml

+name: rta
+channels:
+  - default
+dependencies:
+  # HiPeRTA need to be installed before
+  - python=3.7
+  - numpy~=1.20.1
+  - pip=20.2.1
+  - pip:
+      - https://github.com/garciagenrique/cta-lstchain/archive/refs/tags/v0.1-rta.tar.gz
+      - https://github.com/cta-observatory/ctapipe_io_lst/archive/refs/tags/v0.5.3.tar.gz
+      - https://github.com/cta-observatory/ctapipe-extra/archive/v0.3.1.tar.gz
\ No newline at end of file