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

packages/mansplain.nix

@@ -0,0 +1,18 @@
+# https://www.youtube.com/watch?v=8E8sUNHdzG8
+{
+  writers,
+  man-db,
+  dmenu,
+  gnused,
+  findutils,
+  coreutils,
+  zathura,
+}:
+writers.writeDashBin "mansplain" ''
+  ${man-db}/bin/man -k . \
+    | ${coreutils}/bin/cut -d" " -f1,2 \
+    | ${dmenu}/bin/dmenu -l 5 \
+    | ${gnused}/bin/sed 's/\(.*\) (\(.*\))/\2 \1/' \
+    | ${findutils}/bin/xargs -r ${man-db}/bin/man -t \
+    | ${zathura}/bin/zathura -
+''