[DOC] added post-processing notes in tutorial

[nshahpazov]

Reference Issues/PRs

• [DOC] add explanation of dunder method construction and postprocessing in pipelines to forecasting tutorial #2608

Description of PR

• Checked and confirmed that dunder pipeline methods are described in the tutorial
• Added myself to the list of contributors.
• Added description in the tutorial on how TransformedTargetForecaster can also end with a post-processing Transformer, in this case, I've used a simple predictions rounding

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[fkiraly]

That´s nice, thanks!

May I ask for one thing, to keep the repository size small: can you make sure only the parts are changed where you add content?

I think the current huge diff comes from you rerendering plots.

Worst case, this might require going into the ipynb file with an editor, but should also work if you take the original file and copy-paste the change.

[nshahpazov]

@fkiraly I've addressed the proposed changes. The actual diff is visible now.

[aiwalter]

also please make sure you run pre-commit bcz linting is failing

[fkiraly]

Thanks! Great idea to add this content, will be useful to our users!

Change requests:

• linting
• I would split the content and introduce it step by step, or it may be confusing if it comes all at once, see suggestion above

[nshahpazov]

@fkiraly I've rephrased the paragraphs into three sections like you suggested. Linting is working now. Let me know if you find it ok.

[fkiraly]

All good! Just made some minor changes in formatting.