docs: fix internal links

Fixes #2968.

docs/api/Output.md

@@ -211,8 +211,8 @@ be more than one. The attributes of that element contain:
  * `ref` - content of `ref` tag if it exists
  * `lat`, `lon` - latitude and longitude of the centroid of the object
  * `boundingbox` - comma-separated list of corner coordinates ([see notes](#boundingbox))
- * `place_rank` - class [search rank](../customize/Ranking#search-rank)
- * `address_rank` - place [address rank](../customize/Ranking#address-rank)
+ * `place_rank` - class [search rank](../customize/Ranking.md#search-rank)
+ * `address_rank` - place [address rank](../customize/Ranking.md#address-rank)
  * `display_name` - full comma-separated address
  * `class`, `type` - key and value of the main OSM tag
  * `importance` - computed importance rank

docs/api/Reverse.md

@@ -35,7 +35,7 @@ Additional parameters are accepted as listed below.
 
 !!! warning "Deprecation warning"
     The reverse API used to allow address lookup for a single OSM object by
-    its OSM id. This use is now deprecated. Use the [Address Lookup API](../Lookup)
+    its OSM id. This use is now deprecated. Use the [Address Lookup API](Lookup.md)
     instead.
 
 ### Output format

docs/customize/Importance.md

@@ -12,7 +12,7 @@ customize them.
 The main value for importance is derived from page ranking values for Wikipedia
 pages for a place. For places that do not have their own
 Wikipedia page, a formula is used that derives a static importance from the
-places [search rank](../customize/Ranking#search-rank).
+places [search rank](../customize/Ranking.md#search-rank).
 
 In a second step, a secondary importance value is added which is meant to
 represent how well-known the general area is where the place is located. It