Added unit tests to repo

Closes #10 (closed)

This MR addresses the need for the automated unit tests requested through Anders' software review #1 (closed) .

There are a couple remaining blockers in the implementation of these units tests - mainly, getting git-ci.yml to pass 😓 - but until that is resolved, this MR can still be reviewed and tested by a reviewer locally.

In this MR, I've added 4 scripts in the new folder tests/. Each script test respective functions that are in src/ folder. Each test script is fairly simple right now. I don't think we need to add too much to it, but feel free to suggest additional unit tests to add as asserts. I also added a conftest.py script in the root dir. This script is used to set configurations for pytest, I added it to add the specific path to the functions in the event that I want to test a specific tests/test_*.py script.

I also committed a new empty folder in `tests/` called working_files that serves as the location for the outputs of the test functions. (note that I am hoping to move this to a temp folder that is created and removed in the git-ci.yml but I will not do this until the ci passes and I can get the environment built in gitlab).

How to Review:

To review the new unit test scripts, please:

1. pull this branch

2. rebuild the env (I changed the name to hyswap-geospatial-data-assembly-env and edited a couple libraries)

3. run pytest in the gitbash command line, OR run pytest tests/test_*.py to test a specific test script).

4. Check that the tests pass. You should see a output in the console like this:

   (hyswap-geospatial-data-assembly-env) IGSARMEWLTMSLE:/ msleckman$ pytest
   ====================================================================================================== test session starts ======================================================================================================
   platform darwin -- Python 3.11.6, pytest-8.1.1, pluggy-1.5.0
   rootdir: ~/hyswap-geospatial-data-assembly
   plugins: anyio-4.3.0, requests-mock-1.12.1
   collected 4 items                                                                                                                                                                                                               
   
   tests/test_collate_drainage_area.py .                                                                                                                                                                                     [ 25%]
   tests/test_create_geom_inter.py .                                                                                                                                                                                         [ 50%]
   tests/test_fetch_nhdplus.py .                                                                                                                                                                                             [ 75%]
   tests/test_fetch_states.py .                                                                                                                                                                                              [100%]
   
   ======================================================================================================= warnings summary ========================================================================================================
   ~/miniconda3/envs/hyswap-geospatial-data-assembly-env/lib/python3.11/site-packages/sciencebasepy/SbSession.py:17
   ~/envs/hyswap-geospatial-data-assembly-env/lib/python3.11/site-packages/sciencebasepy/SbSession.py:17: DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html
       from pkg_resources import get_distribution
   
   src/collate_drainage_area_basins.py:4
   ~/hyswap-geospatial-data-assembly/src/collate_drainage_area_basins.py:4: DeprecationWarning: GeoPandas is set to use PyGEOS over Shapely. PyGEOS support is deprecatedand will be removed in GeoPandas 1.0, released in the Q1 of 2024. Please migrate to Shapely 2.0 (https://geopandas.org/en/stable/docs/user_guide/pygeos_to_shapely.html).
       import geopandas as gpd
   
   -- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
   =========================================================================================== 4 passed, 2 warnings in 116.86s (0:01:56) ===========================================================================================

Next issues to address:

• As mentioned, the environment.yml is not successfully building in git-ci.yml. I am able to build it locally however. I believe this is due to the build of pynhd=0.15.2. Next mr should work to address this.
• Clean some packages we absolutely DO NOT need in the environment yml. This should be addressed through #9 (closed)