Move overlays into their own dirs

overlays/srv/default.nix

@@ -0,0 +1,22 @@
+{ lib, fetchFromGitHub, buildGoModule }:
+
+buildGoModule rec {
+  pname = "srv";
+  version = "v0.1.2";
+
+  vendorSha256 = "sha256-ebumpo9hgr7A+Fsznga4ksYu4mcOIfaaKz0uJu2rivE=";
+
+  src = fetchFromGitHub {
+    owner = "davegallant";
+    repo = "srv";
+    rev = version;
+    sha256 = "sha256-x5l/NFEbbRPMBY061g4qRHYV6QUShO7yHqSw+Hir9M0=";
+  };
+
+  meta = with lib; {
+    description = "a simple rss viewer";
+    license = licenses.unlicense;
+    maintainers = with maintainers; [ davegallant ];
+    platforms = platforms.linux ++ platforms.darwin;
+  };
+}