Split the monolithic workflow into specific ones (#1149)

* Split the monolithic workflow into specific ones

* Rename workflows, improve commands

* Update pip from the venv

* Fix Windows setup

* Lowercase macos-latest

* Fix Windows run, again

.github/workflows/code-style.yml

@@ -0,0 +1,21 @@
+name: Code style
+
+on:
+  pull_request:
+    paths:
+      - .github/workflows/code-style.yml
+      - extras/*.py
+      - httpie/**/*.py
+      - setup.py
+      - tests/**/*.py
+
+jobs:
+  code-style:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-python@v2
+        with:
+          python-version: 3.9
+      - run: make venv
+      - run: make codestyle