rudimentary solve for issues #4108, #10256 - "Allow dotnet watch to run external tools"

[Beej126]

corresponds to issues: #4108, #10256 (which are locked so we can't post there)
the basic idea is monitor the dotnet watch run stdout and trigger other tool accordingly.
see powershell script here:
https://gist.github.com/Beej126/e9812b583d1e912a6a08e1af0576975f#file-dotnet_watch_monitor-ps1

example run:

~\source\repos\KingCounty\Kraken\KrakenStack\API [dev ≡ +3 ~6 -2 !]
> .\dotnet_watch_monitor.ps1

Press any key to abort the watcher
[01/30/2021 13:00:33] watch : Started
[01/30/2021 13:00:47] watch : Exited
[01/30/2021 13:00:47] watch : File changed: C:\Users\Beej\source\repos\KingCounty\Kraken\KrakenStack\API\KrakenStack.ServiceModel\Locators.cs
regenerating typescript definitions...
[01/30/2021 13:00:47] watch : Started
Updated: dtos.ts
Everything has been cleanly shut down. Bye =)