Improve longDescription in nixpkgs

[OleMussmann]

The formatting is not preserved:

# package.nix

Find SEARCH_TERM in available nix packages and sort results by relevance.
                                                                                                               
List up to three columns, the latter two being optional:
PACKAGE_NAME  <PACKAGE_VERSION>  <PACKAGE_DESCRIPTION>
                                                                                                               
Matches are sorted by type. Show 'indirect' matches first, then 'direct' matches, and finally 'exact' matches.
                                                                                                               
  indirect  fooSEARCH_TERMbar (SEARCH_TERM appears in any column)
  direct    SEARCH_TERMbar (PACKAGE_NAME starts with SEARCH_TERM)
  exact     SEARCH_TERM (PACKAGE_NAME is exactly SEARCH_TERM)

vs

# https://search.nixos.org

Find SEARCH_TERM in available nix packages and sort results by relevance.

List up to three columns, the latter two being optional: PACKAGE_NAME <PACKAGE_VERSION> <PACKAGE_DESCRIPTION>

Matches are sorted by type. Show ‘indirect’ matches first, then ‘direct’ matches, and finally ‘exact’ matches.

indirect fooSEARCH_TERMbar (SEARCH_TERM appears in any column) direct SEARCH_TERMbar (PACKAGE_NAME starts with SEARCH_TERM) exact SEARCH_TERM (PACKAGE_NAME is exactly SEARCH_TERM)