Do not write inventory if Documenter can do it

Just skip writing the inventory if the function
`Documenter.HTMLWriter.write_inventory` exists, indicating that
the installed version of Documenter can write inventories itself.

For compatibility with
JuliaDocs/Documenter.jl#2424

Project.toml

@@ -1,7 +1,7 @@
 name = "DocumenterInterLinks"
 uuid = "d12716ef-a0f6-4df4-a9f1-a5a34e75c656"
 authors = ["Michael Goerz <mail@michaelgoerz.net>"]
-version = "0.2.4"
+version = "0.2.4+dev"
 
 [deps]
 CodecZlib = "944b1d66-785c-5afd-91f1-9de20f533193"

src/write_inventory.jl

@@ -28,8 +28,12 @@ function Selectors.matcher(::Type{WriteInventory}, doc::Documenter.Document)
 end
 
 function Selectors.runner(::Type{WriteInventory}, doc::Documenter.Document)
-    @info "WriteInventory: writing `objects.inv` and `inventory.toml.gz` file."
-    write_inventory(doc)
+    if isdefined(Documenter.HTMLWriter, :write_inventory)
+        @debug "Skip writing inventories in DocumenterInterLinks: handled by Documenter"
+    else
+        @info "WriteInventory: writing `objects.inv` and `inventory.toml.gz` file."
+        write_inventory(doc)
+    end
 end