Add a "note" to a GIT commit

Question

One of the key issues I keep having at my work, is to keep track which GIT commit corresponds with the update at customer premises.

... and now I think "But what if I could add a note (like a note, added at an Excel cell), something like this:

Does such a thing already exists in GIT/GIT Extensions?

Edit: There already exists a 'notes' feature, but how to use it?
I'd like to thank phd and hlovdal for your very quick response. Apparently there is a "Notes" feature, and I can confirm that my GIT installation knows about it, as can be seen from this GIT BASH excerpt:

<GIT Repository> (master)
$ git notes show
error: no note found for object c1ead08e97978300e4b703eb29d64782b6361062.

=> "Notes" seems to exist, but is it possible to execute a "Notes"-related command without error?

<GIT Repository> (master)
$ git notes list

=> Yes, it is possible to execute a "Notes"-related command without error.

<GIT Repository> (master)
$ git blabla
git: 'blabla' is not a git command. See 'git --help'.

=> Anyway, if it did not exist, this would have been the result.

... But what about my GIT-Extensions application? Well, I don't find it anywhere, so I looked for it in the helpfile:

My menu looks different than that, but there is a shortcut key Ctrl+Shift+N, let's try it.

Bad idea: my GIT-Extensions application went into "Not reponding", and even although it takes more than 10 minutes to write down this edit, it still is not responding :-)

For your information: I didn't find "Notes" in the Plugin Manager, so how can I install/activate/use it in my GIT-Extensions application?