treewide: convert all option docs to Markdown

This process was automated by [my fork of `nix-doc-munge`]. All
conversions were automatically checked to produce the same DocBook
result when converted back, modulo minor typographical/formatting
differences on the acceptable-to-desirable spectrum.

To reproduce this commit, run:

  $ NIX_PATH=nixpkgs=flake:nixpkgs/e7e69199f0372364a6106a1e735f68604f4c5a25 \
    nix shell nixpkgs#coreutils \
    -c find . -name '*.nix' \
    -exec nix run -- github:emilazy/nix-doc-munge/98dadf1f77351c2ba5dcb709a2a171d655f15099 \
    {} +
  $ ./format

[my fork of `nix-doc-munge`]: https://github.com/emilazy/nix-doc-munge/tree/home-manager

modules/programs/astroid.nix

@@ -55,13 +55,13 @@ let
 in {
   options = {
     programs.astroid = {
-      enable = mkEnableOption "Astroid";
+      enable = mkEnableOption (lib.mdDoc "Astroid");
 
       pollScript = mkOption {
         type = types.str;
         default = "";
         example = "mbsync gmail";
-        description = ''
+        description = lib.mdDoc ''
           Script to run to fetch/update mails.
         '';
       };
@@ -104,7 +104,7 @@ in {
             poll.interval = 0;
           }
         '';
-        description = ''
+        description = lib.mdDoc ''
           JSON config that will override the default Astroid configuration.
         '';
       };