Added shell to markdown code blocks

docs/building.markdown

@@ -8,7 +8,7 @@ permalink: /building/
 
 cmkr requires a C++11 compiler, cmake >= 3.15.
 
-```
+```sh
 git clone https://github.com/build-cpp/cmkr
 cd cmkr
 cmake -Bbin

docs/usage.markdown

@@ -39,6 +39,6 @@ arguments:
 
 The build command invokes cmake and the default build-system on your platform (unless a generator is specified), it also accepts extra cmake build arguments:
 
-```
+```sh
 cmkr build --config Release 
 ```