ENH: add contextmanager to HDFStore (#8791)

Added a context manager to HDFStore

closes #8791
I think we should add here something to the docstring of `get_store` that is is an alias of HDFStore -> better to use that. 
You can use pd.util.decorators.Appender for that. Something like:

```
get_store = Appender("Backwards compatible alias for ``HDFStore``", join='\n')(HDFStore)
```