Import Help 1.1.0: doc, doc_items, doc_identifier

mods/HELP/doc/doc_identifier/API.md

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+# Minimal API for `doc_identifier`
+## Introduction
+The tool can identify blocks and players natively, and also handles falling
+nodes (`__builtin:falling_node`) and dropped items (`__builtin:item`) on its
+own.
+
+However, the identifier can't “identify” (=open the appropriate entry) custom
+objects because the mod doesn't know which help entry to open (if there is
+any). One example would be the boat object (`boats:boat`) from the boats mod
+in Minetest Game.
+If the player tries to use the tool on an unknown object, an error message is
+shown.
+
+Because of this, this mod provides a minimal API for mods to assign a help
+entry to an object type: `doc_identifier.register_object`.
+
+## `doc.sub.identifier.register_object(object_name, category_id, entry_id)`
+Registers the object/entity with the internal name `object_name` to the
+entry `entry_id` in the category `category_id`.
+It is in the modder's responsibility to make sure that both the category and
+entry already exist (use `doc.entry_exists` or depend (optionally or not) on
+the respective mods) at the time of the function call, otherwise, stability can
+not be guaranteed.
+
+Returns `nil`.
+
+### Example
+From `doc_minetest_game`:
+
+    if minetest.get_modpath("doc_identifier") ~= nil then
+        doc.sub.identifier.register_object("boats:boat", "craftitems", "boats:boat")
+    end
+
+This enables the tool to be used on the boat object itself. The conditional is
+an idiom to check for the existence of this mod.
+
+## Note on dependencies
+If you just need `doc.sub.identifier.register_object` using only an **optional**
+dependency for your mod is probably enough.
+