Add chun_codes to docs/requirements.txt

 - Use editable option of pip
 - Simplify sphinx-build GitHub actions

.github/workflows/sphinx-build.yml

@@ -12,26 +12,10 @@ on:
 jobs:
   docs:
     runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        python-version: ['3.8']
 
     steps:
-    - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v2
-      with:
-        python-version: ${{ matrix.python-version }}
     - name: Checkout MSC
       uses: actions/checkout@v2
-    - name: Checkout chun_codes
-      uses: actions/checkout@v2
-      with:
-        repository: astrochun/chun_codes
-        path: chun_codes
-    - name: Install chun_codes
-      run: |
-        python setup.py install
-      working-directory: chun_codes
     - name: Sphinx build
       uses: ammaraskar/sphinx-action@master
       with:

docs/requirements.txt

@@ -1,3 +1,4 @@
 sphinx>=3.0
 sphinx-rtd-theme==0.5.1
 sphinx-autodoc-typehints==1.11.1
+-e git+https://github.com/astrochun/chun_codes.git#egg=chun_codes