ENH: Auto Detect engine in read_excel
- [x] I have checked that this issue has not already been reported.

- [x] I have confirmed this bug exists on the latest version of pandas.

- [ ] (optional) I have confirmed this bug exists on the master branch of pandas.

---

**Note**: Please read [this guide](https://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports) detailing how to provide the necessary information for us to reproduce your bug.

#### Code Sample, a copy-pastable example

This works:

```python
import pandas as pd
df = pd.read_excel('Book2.xlsb', engine='pyxlsb')
```

This doesn't:

```python
import pandas as pd
df = pd.read_excel('Book2.xlsb')
```

#### Problem description

All supported Excel formats (`xls`, `xlsx`, `xlsm`) have a default engine based on the extension, so you can simply do:

```
df = pd.read_excel('Book2.xlsx')
```

For `xlsb`,  when you do `df = pd.read_excel('Book2.xlsb')`, you get this error:

```
XLRDError: Excel 2007 xlsb file; not supported
```

#### Expected Output

No error, i.e. it should figure out that for `xlsb` extensions, `pyxlsb` is the default engine.

#### Output of ``pd.show_versions()``

<details>

INSTALLED VERSIONS
------------------
commit           : None

pandas           : 1.0.5
numpy            : 1.18.1
pytz             : 2020.1
dateutil         : 2.8.1
pip              : 20.0.2
setuptools       : 49.2.0.post20200714
Cython           : None
pytest           : 5.4.3
hypothesis       : None
sphinx           : 2.4.0
blosc            : None
feather          : None
xlsxwriter       : 1.2.7
lxml.etree       : None
html5lib         : None
pymysql          : None
psycopg2         : None
jinja2           : 2.11.2
IPython          : 7.16.1
pandas_datareader: None
bs4              : None
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : None
matplotlib       : 3.1.3
numexpr          : None
odfpy            : None
openpyxl         : 3.0.4
pandas_gbq       : None
pyarrow          : 0.17.1
pytables         : None
pytest           : 5.4.3
pyxlsb           : 1.0.6
s3fs             : None
scipy            : 1.4.1
sqlalchemy       : None
tables           : None
tabulate         : 0.8.7
xarray           : None
xlrd             : 1.2.0
xlwt             : 1.3.0
xlsxwriter       : 1.2.7
numba            : None

</details>
