Added building page

docs/building.markdown

@@ -0,0 +1,16 @@
+---
+layout: page
+title: Building
+permalink: /building/
+---
+
+## Building
+
+cmkr requires a C++11 compiler, cmake >= 3.15.
+
+```
+git clone https://github.com/build-cpp/cmkr
+cd cmkr
+cmake -Bbin
+cmake --build bin --parallel
+```