DOC: add examples to offsets CustomBusinessDay, Business/MonthBegin
This pr is related to pr #50182, #49958 and #50027.
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).

Updated docs for `BusinessMonthBegin`, `CustomBusinessDay` and `MonthBegin`. Added more examples to highlight “the first day of the month” behavior. Gave examples that use the parameter n equals 0. Provided more examples for CustomBusinessDay parameters weekmask and calendar.
Hi @MarcoGorelli. I updated documentation for `CustomBusinessDay`, `BusinessMonthBegin` and `MonthBegin.` Corrected lists of parameters and provided more examples.
Could you, please, take a look at this PR? /preview Website preview of this PR available at: https://pandas.pydata.org/preview/51932/ Looks like ci failures are related to my new example for offset. 
```
D:\a\pandas\pandas\pandas\_libs\tslibs\src\datetime\np_datetime.c : fatal error C1083: Cannot open compiler generated file: 'D:\a\pandas\pandas\build\temp.win-amd64-cpython-39\Release\pandas\_libs\tslibs\src\datetime\np_datetime.obj': Permission denied
```
[link](https://github.com/pandas-dev/pandas/actions/runs/4421396269/jobs/7752145291#step:4:1267)

I use Linux and can’t catch errors raised for windows platform.

There is a Timedelta function in pandas, which shifts days as well and I can use this one.
`pd.Timestamp(2022, 8, 5, 16) + pd.offsets.CustomBusinessDay(1, offset=pd.Timedelta(days=1))`
Will it work for `windows?`
 > Website preview of this PR available at: https://pandas.pydata.org/preview/51932/

Nice, thank you!  > Looks like ci failures are related to my new example for offset.

it's unrelated, it happens before even having finished compiling pandas (which isn't affected by docstrings)