Fix multi-line doc generation

When generating a parameter list item the doc generator now indents the rest of the docstring to match the level of the list item.

examples:

* `resources_from_deps`: Set of build targets whose transitive `apple_resource`s should be considered as part of the current resource when collecting resources for bundles.

  Usually, an `apple_bundle` collects all `apple_resource` rules transitively
  reachable through apple\_library rules. This field allows for resources which are not reachable
  using the above traversal strategy to be considered for inclusion in the bundle.

* `asset_catalogs_compilation_options`: A dict holding parameters for asset catalogs compiler (actool). Its options include:

  * `notices` (defaults to `True`)
  * `warnings` (defaults to `True`)
  * `errors` (defaults to `True`)
  * `compress_pngs` (defaults to `True`)
  * `optimization` (defaults to `'space'`)
  * `output_format` (defaults to `'human-readable-text'`)
  * `extra_flags` (defaults to `[]`)
* `deps`: A list of dependencies of this bundle as build targets. You can embed application extensions by specifying the extension's bundle target. To include a WatchKit app, append the flavor `#watch` to the target specification. Buck will automatically substitute the appropriate platform flavor (either `watchsimulator` or `watchos`) based on the parent.

* `header_path_prefix`: A path prefix when including headers of this target. For example, headers from a library defined using

apple_library( name = "Library", headers = glob(["*/.h"]), header_path_prefix = "Lib", )


  can be imported using following mapping

Library/SubDir/Header1.h -> Lib/Header1.h Library/Header2.h -> Lib/Header2.h


  Defaults to the short name of the target. Can contain forward slashes (`/`), but
   cannot start with one. See `headers` for more information.

facebook / buck2

Fix multi-line doc generation #559