Add basic CMake github action

.github/workflows/cmake.yml

@@ -0,0 +1,26 @@
+name: CMake
+
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "master" ]
+
+jobs:
+  linux-build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4.1.1
+
+    - name: CMake workflow
+      run: cmake --workflow --preset default
+
+  windows-build:
+    runs-on: windows-latest
+
+    steps:
+    - uses: actions/checkout@v4.1.1
+
+    - name: CMake workflow
+      run: cmake --workflow --preset default

ReadMe.md

@@ -1,5 +1,6 @@
-[![Travis Build Status](https://api.travis-ci.org/LegalizeAdulthood/iterated-dynamics.png?branch=master)](https://travis-ci.org/LegalizeAdulthood/iterated-dynamics)
-[![Appveyor Build status](https://ci.appveyor.com/api/projects/status/0k69hj9n28u0c3rj?svg=true)](https://ci.appveyor.com/project/LegalizeAdulthood/iterated-dynamics)
+[![CMake workflow](https://github.com/LegalizeAdulthood/iterated-dynamics/actions/workflows/cmake.yml/badge.svg)](https://github.com/LegalizeAdulthood/iterated-dynamics/actions/workflows/cmake.yml)
+
+# Iterated Dynamics
 
 Iterated Dynamics is an open source fractal renderer that can generate
 the following fractal types: