riemann-tools: add meta-data

see issue #43716

pkgs/tools/misc/riemann-tools/default.nix

···
-{ bundlerEnv }:
+{ stdenv, bundlerEnv }:
 
 bundlerEnv {
   name = "riemann-tools-0.2.13";
   gemfile = ./Gemfile;
   lockfile = ./Gemfile.lock;
   gemset = ./gemset.nix;
+
+  meta = {
+    description = "Tools to submit data to Riemann";
+    homepage = "https://riemann.io";
+    license = stdenv.lib.licenses.mit;
+  };
 }