GitHub Action to pip install symengine on current Python and PyPy

* symengine#421

Author: cclauss

.github/workflows/pip_install.yml

@@ -0,0 +1,16 @@
+name: pip_install
+on: [pull_request, push]
+jobs:
+  pip_install:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest]  # [ubuntu-latest, macos-latest, windows-latest]
+        python-version: ['3.8', '3.9', '3.10', '3.11', '3.12', 'pypy3.9', 'pypy3.10']
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/setup-python@v4
+        with:
+          python-version: ${{ matrix.python-version }}
+      - run: pip install --upgrade pip setuptools wheel
+      - run: pip install symengine