add vertical and horizaontal symbol

[kevinsmia1939]

Detail the reasoning behind the code change. If there is an associated issue that this PR will resolve add

This PR add vertical and horizontal symbol.

Fixes #

Other Tasks

Bump Dependency Versions

Files that need updates

Confirm the following files have been either updated or there has been a determination that no update is needed.

• README.md
• setup.py
• tox.ini
• .github/workflows/main.yml and associated requirements.txt and conda environemt.yml files
• pyproject.toml
• binder/requirements.txt

Pre-Release Checklist

Pre Release Checklist

• Update version info in __init__.py
• Update CHANGELOG primarily using contents from automated changelog generation in GitHub release page
• Have git tag in the format of pyqtgraph-

Post-Release Checklist

Steps To Complete

• Append .dev0 to __version__ in __init__.py
• Announce on mail list
• Announce on Twitter

[pijyoi]

I see that you have used the same mnemonics as matplotlib
(https://matplotlib.org/stable/api/markers_api.html)

Could you add your new symbols to:
https://github.com/pyqtgraph/pyqtgraph/blob/master/pyqtgraph/examples/Symbols.py

And also update _symbol_pg_to_mpl in:
https://github.com/pyqtgraph/pyqtgraph/blob/master/pyqtgraph/exporters/Matplotlib.py#L32-L50

[j9ac9k]

Superseded by #2985

Thanks for the PR @kevinsmia1939 !