add congratulations at the end of our notebooks

[tchaton]

What does this PR do?

This PR add a message at the end of each notebook

Fixes # (issue)

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[tchaton]

Added this markdown at the end of each notebooks !

[codecov]

Codecov Report

Merging #4555 (c00fe4f) into master (6e5f232) will decrease coverage by 0%.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #4555   +/-   ##
======================================
- Coverage      93%     93%   -0%     
======================================
  Files         116     116           
  Lines        8815    8815           
======================================
- Hits         8228    8225    -3     
- Misses        587     590    +3     

[edenlightning]

Until we get https://www.reviewnb.com/ ill just put suggestions here:

1. Some of the exclamation marks can be replaced with colons, "You can do so in the following ways:"
2. Capitalization
3. Add link to slack
4. "Interested in SOTA models? Check out Bolts. Bolts has a collection of models, all implemented in lightning, ...."
5. "Contribute"

• "You can also contribute your own notebooks with useful examples"

[Borda]

@williamFalcon could you pls add it, @teddykoker @edenafek what are the bullet points do so?

[tchaton]