There is one thing I couldn't figure out, however. I want to
    introduce "Object" as a new type tag, so that
             --- Function description
             -- @treturn Object The created object
             blah = function() ...
    makes "Object" a link to a description of the object's structure.
There are a number of ways. If Object is just a table, then add a named
table to that module:
--- About Object.
-- @field name name of person
-- @field age age of person
-- @table Object
That's pretty much how it was done in LuaDoc (except for the @table
shortcut meaning @class table/@name Object)
If it's a 'class', then declare it with the @type tag (we can't use
@class because of LuaDoc compatibility)