add pipe scripts for slack logging

[Hamms]

Description

Adds a couple of scripts that we will be able to use to log the results of the i18n sync to slack. Specifically, each script will pipe any given stdin stream directly to the slack channel appropriate to the environment in which it is being used; one script will display input normally, the other will display input as an error.

This means we can combine these scripts to report both stdout and stderr appropriately. For example, say we have a script like example.rb:

$stdout.puts "stdout"
$stderr.puts "stderr"

We can run this script like ruby example.rb | slack_log to pipe just stdout to slack, or like (ruby example.rb | slack_log) |& slack_error to pipe stdout to slack regularly, and stderr to slack as an error.

Reviewer Checklist:

• Tests provide adequate coverage
• Code is well-commented
• New features are translatable or updates will not break translations
• Relevant documentation has been added or updated
• User impact is well-understood and desirable
• Pull Request is labeled appropriately
• Follow-up work items (including potential tech debt) are tracked and linked

[Hamms]

we could also do something like ruby example.rb > >(slack_log) 2> >(slack_error) to split the output appropriately; it's not clear to me what the relative advantages and disadvantages are of that vs the pipe approach