Fish: `.` is deprecated

[kkebo]

In fish, . is deprecated and will be removed in the future version.

https://fishshell.com/docs/current/cmds/source.html#description

. (a single period) is an alias for the source command. The use of . is deprecated in favour of source, and . will be removed in a future version of fish.

Therefore, in #91, we should have used source /path/to/env.fish instead of . /path/to/env.fish when using fish.