Move elastic constants first in response docs order

Author: niklasschmitz

docs/make.jl

@@ -44,10 +44,10 @@ PAGES = [
         "examples/energy_cutoff_smearing.jl",
     ],
     "Response and properties" => [
+        "examples/elastic_constants.jl",
         "examples/polarizability.jl",
         "examples/forwarddiff.jl",
         "examples/phonons.jl",
-        "examples/elastic_constants.jl",
     ],
     "Ecosystem integration" => [
         # This concerns the discussion of interfaces, IO and integration