Support Python 3.10 (#1591)

* Add Python 3.10 classifier to setup.py. Also changed PyGMT's development status from alpha
to beta.
* Use Python 3.10 for style_checks and publish-to-pypi CI workflows

Author: weiji14

.github/workflows/publish-to-pypi.yml

@@ -31,7 +31,7 @@ jobs:
     - name: Set up Python
       uses: actions/[email protected]
       with:
-        python-version: 3.9
+        python-version: '3.10'
 
     - name: Install dependencies
       run: python -m pip install setuptools wheel

.github/workflows/style_checks.yaml

@@ -22,7 +22,7 @@ jobs:
       - name: Set up Python
         uses: actions/[email protected]
         with:
-          python-version: 3.9
+          python-version: '3.10'
 
       - name: Install packages
         run: |

setup.py

@@ -21,7 +21,7 @@
 PACKAGE_DATA = {"pygmt.tests": ["data/*", "baseline/*"]}
 
 CLASSIFIERS = [
-    "Development Status :: 3 - Alpha",
+    "Development Status :: 4 - Beta",
     "Intended Audience :: Science/Research",
     "Intended Audience :: Developers",
     "Intended Audience :: Education",
@@ -30,6 +30,7 @@
     "Programming Language :: Python :: 3.7",
     "Programming Language :: Python :: 3.8",
     "Programming Language :: Python :: 3.9",
+    "Programming Language :: Python :: 3.10",
     f"License :: OSI Approved :: {LICENSE}",
 ]
 PLATFORMS = "Any"