[doc, plugin] Exporter: manually specify module name (#10465)

Follow-up to <https://github.com/koreader/koreader/pull/10464>.

plugins/exporter.koplugin/main.lua

@@ -1,4 +1,4 @@
---[[
+--[[--
 Export highlights to different targets.
 
 Some conventions:
@@ -22,7 +22,8 @@
 
 - Booknotes: Every table in clippings table. clippings = {"title" = booknotes}
 
---]]
+@module koplugin.exporter
+--]]--
 
 local DataStorage = require("datastorage")
 local Device = require("device")
@@ -174,7 +175,7 @@ function Exporter:exportAllNotes()
 end
 
 --- Parse and export highlights from selected documents.
--- @tparam table files list of files 'file_path = true'
+-- @tparam table files list of files as a table of {[file_path] = true}
 function Exporter:exportFilesNotes(files)
     local clippings = self.parser:parseFiles(files)
     for title, booknotes in pairs(clippings) do