docs: link methods in Etag section

Signed-off-by: Viktor Diezel <viktor.diezel@posteo.de>

Author: vdiezel

docs/API.md

@@ -101,14 +101,14 @@ curl -u admin:admin -X GET \
 
 An ETag header is returned in order to determine if further child elements have been updated for the following endpoints:
 
-- Fetch all user board `GET /api/v1.0/boards`
-- Fetch a single board `GET /api/v1.0/boards/{boardId}`
-- Fetch all stacks of a board `GET /api/v1.0/boards/{boardId}/stacks`
-- Fetch a single stacks of a board `GET /api/v1.0/boards/{boardId}/stacks/{stackId}`
-- Fetch a single card of a board `GET /api/v1.0/boards/{boardId}/stacks/{stackId}/cards/{cardId}`
-- Fetch attachments of a card `GET /api/v1.0/boards/{boardId}/stacks/{stackId}/cards/{cardId}/attachments`
-
-If a `If-None-Match` header is provided and the requested element has not changed a `304` Not Modified response will be returned.
+- [List user boards](#list-boards)
+- [Get board by ID](#get-board)
+- [List board stacks](#list-stacks)
+- [Get stack by ID](#get-stack)
+- [Get card by ID](#get-card)
+- [List card attachments](#list-attachments)
+
+If a `If-None-Match` header is provided and the requested element has not changed a `304 Not Modified` response will be returned.
 
 Changes of child elements will propagate to their parents and also cause an update of the ETag which will be useful for determining if a sync is necessary on any client integration side. As an example, if a label is added to a card, the ETag of all related entities (the card, stack and board) will change.