DOC: update cheatsheet
- [x] closes #39724
- [x] tests added / passed  (not required)
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them  (not required)
- [x] whatsnew entry (not required)



#### Major changes

1) **Replaced Heading "Data Wrangling ..." with section "General"**
   - I found it useful to have the hyperlinks to pandas api reference and user guide included
   - Also, all the time time when you work with pandas you need other packages (matplotlib etc.). That's why added hyperlinks for them as well
   - There is some place left for other useful links!
2) **Replaces explanatory section "Tidy data" with  section "Display & Visualize data"**
   - Cheat sheets are for users who already have basic knowledge. So this explanation of Tidy Data is of no use here
   - Displaying and visualizing data is one of the main tasks. So this section should be included in the cheat sheet
   - On the previous cheat sheet there also was a section "Plotting". But it was very small at the end of the second page.
3) **Added section "Apply Funtions"** (bottom of second page)
   - There are many ways to apply functions and I always find it confusing to remember them. So I added them here with a short description
   - However, if you have a better suggestion for this section, it can be interchanged
4) **Refractor section "Subset Observation"**
   - This section was pretty confusing in styling and layout before. E.g. there where multiple places where you can find the df.loc[]  and df.iloc [] functions.
   - I reordered this section
   - I added df.iloc[row_ind, column_ind] and df.loc[row_ind, column_ind]

Let me know what you think about it and make suggestions.
Oli