feat: fix secrets permissions, move ./packages to flake outputs

packages/rfc.nix

@@ -0,0 +1,23 @@
+{
+  writers,
+  curl,
+  pup,
+  gawk,
+  gnused,
+  gnugrep,
+  less,
+  fzf,
+}:
+writers.writeDashBin "rfc" ''
+  set -efu
+  selection=$(
+    ${curl}/bin/curl -sSL https://www.rfc-editor.org/rfc-index.txt \
+    | ${gawk}/bin/awk '/^$/{print;} /./{printf("%s ", $0);}' \
+    | ${gnused}/bin/sed 's/\s\+/ /g' \
+    | ${gnused}/bin/sed -n '/^[0-9]\+ /,$p' \
+    | ${fzf}/bin/fzf \
+    | ${gawk}/bin/awk '{print $1}'
+  )
+
+  ${curl}/bin/curl -sSL "https://www.rfc-editor.org/rfc/rfc$selection.txt" | ${less}/bin/less
+''