[Added] Doc on generating Code128 Barcode

[ssavi-ict]

• Fixes Doc: provide an usage example of combining fpdf2 with python-barcode #720
• Added Code128 Barcode documentation.

Checklist:

• The GitHub pipeline is OK (green),
  meaning that both pylint (static code analyzer) and black (code formatter) are happy with the changes of this PR.

• A unit test is covering the code added / modified by this PR

• This PR is ready to be merged

• In case of a new feature, docstrings have been added, with also some documentation in the docs/ folder

• A mention of the change is present in CHANGELOG.md

By submitting this pull request, I confirm that my contribution is made under the terms of the GNU LGPL 3.0 license.

[ssavi-ict]

@Lucas-C, Please have a look at this PR. And let me know of any further issues.

Thank You.

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (338977a) 92.70% compared to head (36906da) 92.70%.

❗ Current head 36906da differs from pull request most recent head c897247. Consider uploading reports for the commit c897247 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #746   +/-   ##
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  Coverage   92.70%   92.70%           
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  Files          27       27           
  Lines        7266     7266           
  Branches     1313     1313           
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  Hits         6736     6736           
  Misses        336      336           
  Partials      194      194           

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[Lucas-C]

This is perfect!
Thank you @ssavi-ict 😊
Merging now

[Lucas-C]

@allcontributors please add @ssavi-ict for documentation

[allcontributors]

@Lucas-C

I've put up a pull request to add @ssavi-ict! 🎉

[Lucas-C]

Congratulations, it's published in fpdf2 documentation! 😊
https://pyfpdf.github.io/fpdf2/Barcodes.html#code128