Zodipy

- Added possibility to select between modern solar irradiance models for computing the scattered solar emission. These can be selected by specifying the `solar_irradiance_model` argument when initializing `Zodipy`.
- Zodipy now throws an error by default if the selected frequency or wavelength is outside of the range covered by the selected interplanetary dust model. To linearly extrapolate the spectral parameters in the model, set `extarpolate=True` when initializing `Zodipy`.
- Improved performance is achieved by introducing [quadpy](https://pypi.org/project/quadpy/) as a new dependency, which speeds up the line of sight integration.

**This release changes the interface of Zodipy to no longer depend on specific observer/earth position as input, and allows the user to provide pointing information in the form of angular coordinates.**

- *Zodipy* now expects a `str` representing an observer and an `astropy.time.Time` object representing the time of observation instead of the previously required observer and earth positions in AU.
- The pointing information can now be given in the form of angles on the sky in co-latitude and longitude (`theta` and `phi`).
- The JPL ephemeris `de432s` will be downloaded the first time the interface is initialized (10 MB file).

**Following is a new minimal *Zodipy* use case**
python
from astropy import unit as u
from astropy.time import Time
from zodipy import Zodipy

model = Zodipy()
model.get_emission(
25*u.micron,
obs="earth",
obs_time=Time.now(),
theta=10*u.deg,
phi=40*u.deg,
)
>> <Quantity [16.65684599] MJy / sr>

**This release provides a significant upgrades to the Zodipy performance speed (up to 2x from the previous release).**

The performance is mainly the result of e76707cbf91eee76dffef8269cf6aa2620d4e026 where the following changes were made:
1) the Planck function and the Interplanetary temperature is tabulated instead of being computed along each line of sight
2) the software architecture is refactored to remove redundant calculations

**Additionally, the user interface is changed slightly.**
The main interface is now called `Zodipy` and features two methods: `get_time_ordered_emission` and `get_instantaneous_emission`.
Following is an example how to use Zodipy with the new interface:

python
from zodipy import Zodipy

model = Zodipy()
emission = model.get_time_ordered_emission(
25 * u.micron,
nside=256,
pixels=[...],
observer_pos=[...] * u.AU,
)

This release introduces significant changes to the way *Zodipy* is used compared to previous versions.
For a more in-depth guide on how to use *Zodipy* following the changes, see the README.
**Changed**

- The *Zodipy* interface interface is now initialized with the `InterplanetaryDustModel` class instead of `Zodi`.
- Instantaneous emission is now simulated using the `get_instantaneous_emission` method of the interface.
- Time-ordered emission can now be simulated with the `get_time_ordered_emission` method of the interface.

This release updates project dependency versions and introduces unit and type testing

**Changed**

- Updated `pillow` and related dependencies due to invulnerability issues with versions < 8.3.2
- Introduced type checking with `mypy`
- Introduced a few unit tests with `pytest`
- Added GitHub actions to automatically run `pytest` and `mypy` on push and pull requests

**Note: This release only includes code refactoring. The behavior of Zodipy remains the same.**
- Merged the two existing simulation strategies into a common strategy that handles both simulation use cases 43c29ed5ad4ec02bdde5e977f71b7185f16f509e