ENH: format_bytes bool arg in memory_usage?
#### Is your feature request related to a problem?

[this should provide a description of what the problem is, e.g. "I wish I could use pandas to do [...]"]
I wish pandas could return formatted bytes when calling memory_usage so I can easily understand how much memory a column takes up

#### Describe the solution you'd like

```
DataFrame.memory_usage(..., format_bytes: bool = False):
if format_bytes:
    ...
```

#### API breaking implications

None (hopefully). An addition arg which defaults to False 

#### Describe alternatives you've considered

```
from dask.utils import format_bytes
import pandas as pd

df = pd.DataFrame([range(1000), ["a"] * 1000]).T
df.memory_usage()
```

<img width="170" alt="Screen Shot 2021-09-02 at 4 40 16 PM" src="https://user-images.githubusercontent.com/17162724/131913139-8267557e-b5be-42d3-b35d-8271db923a3d.png">


```
df.memory_usage().apply(format_bytes)
```

<img width="415" alt="Screen Shot 2021-09-02 at 4 38 41 PM" src="https://user-images.githubusercontent.com/17162724/131912997-dbb0c86f-4f48-4c1c-982c-4b03dd9d254b.png">


#### Additional context

[add any other context, code examples, or references to existing implementations about the feature request here]

```python
# Your code here, if applicable

```
