Use optional-dependencies for all dependency groups

This moves us away from requirements files and centralizes all
dependency specifications under 'project.optional-dependencies'.

.github/workflows/ci.yml

@@ -23,12 +23,10 @@ jobs:
         with:
           python-version: ${{ matrix.python-version }}
           cache: 'pip'
-          cache-dependency-path: 'tests/requirements.txt'
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip setuptools
-          python -m pip install -r tests/requirements.txt
-          pip install -e .
+          pip install -e .[lint,test,typing]
       - name: Lint
         run: |
           flake8

.readthedocs.yaml

@@ -13,4 +13,5 @@ python:
   install:
     - method: pip
       path: .
-    - requirements: docs/requirements.txt
+      extra_requirements:
+        - docs

pyproject.toml

@@ -23,10 +23,29 @@ classifiers = [
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
 ]
+requires-python = ">= 3.8"
 dependencies = [
     "httpx>=0.23.1",
 ]
-requires-python = ">= 3.8"
+
+[project.optional-dependencies]
+docs = [
+    "Sphinx==7.2.2",
+    "furo==2023.9.10",
+]
+lint = [
+    "black==23.12.0",
+    "flake8==7.0.0",
+    "isort==5.13.0",
+]
+test = [
+    "pytest==7.4.0",
+    "pytest-cov==4.1.0",
+    "respx==0.20.1",
+]
+typing = [
+    "mypy==1.8.0",
+]
 
 [project.urls]
 Homepage = "https://github.com/jparise/vesta"