ENH: Add scraper sync note

[adamovanja]

This PR:

• adds a note for how the user can make sure the scrape-collection action is run properly.
• adjusts the warning that is raised in case no attachments were found.

[codecov[bot]]

Codecov Report

Merging #153 (c7ead1b) into main (71727c1) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #153   +/-   ##
=======================================
  Coverage   98.62%   98.62%           
=======================================
  Files          29       29           
  Lines        2980     2980           
=======================================
  Hits         2939     2939           
  Misses         41       41           

Impacted Files	Coverage Δ
q2_fondue/scraper.py	100.00% <ø> (ø)
q2_fondue/tests/test_scraper.py	100.00% <ø> (ø)

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