Add iTerm2 snowflake (macOS support)

Since Tilix (1) is designed for Linux the most popular macOS terminal
emulator iTerm2 (2) will be used as replacement. This snowflake should
includes the exported JSON file of the created `igloo` profile.

References:

  (1) https://github.com/gnunn1/tilix
  (2) https://www.iterm2.com

Epic: GH-131
Related to GH-70
Closes GH-135