Watch: listen for new files

[dmitrage]

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

List any relevant issue numbers:
#3704

Description

As suggested in the linked issue.

After I added the second test I discovered that it passes without this patch as well but decided to keep it to be sure.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@929f0ac). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #3812   +/-   ##
=========================================
  Coverage          ?   97.03%           
=========================================
  Files             ?      185           
  Lines             ?     6477           
  Branches          ?     1876           
=========================================
  Hits              ?     6285           
  Misses            ?      101           
  Partials          ?       91           

Impacted Files	Coverage Δ
src/watch/fileWatcher.ts	96.42% <ø> (ø)

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[lukastaegert]

Awesome work, thanks a lot! Will release this soon.