DOC: Add number of errors/warnings 
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

Add number of Errors or Warnings to scripts/validate_docstrings.py when validating docstrings.
Hello @hongshaoyang! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`scripts/validate_docstrings.py`](https://github.com/hongshaoyang/pandas/blob/ccb4a9d2187f76c1375682107f47c8cdc61ea9de/scripts/validate_docstrings.py) !

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23150?src=pr&el=h1) Report
> Merging [#23150](https://codecov.io/gh/pandas-dev/pandas/pull/23150?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/21e8522102c334acb79dd4a7b3f7a914af535a8e?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23150/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23150?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #23150   +/-   ##
=======================================
  Coverage   92.13%   92.13%           
=======================================
  Files         170      170           
  Lines       51073    51073           
=======================================
  Hits        47056    47056           
  Misses       4017     4017
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.56% <ø> (ø)` | :arrow_up: |
| #single | `42.28% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23150?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23150?src=pr&el=footer). Last update [21e8522...ccb4a9d](https://codecov.io/gh/pandas-dev/pandas/pull/23150?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks!