Add header target for 1D tutorial

Author: basnijholt

docs/source/index.md

@@ -16,7 +16,7 @@ end-before: <!-- summary-end -->
 ```
 
 ```{tip}
-[Click here](https://adaptive.readthedocs.io/en/latest/tutorial/tutorial.Learner1D.html) to start with the 1D function learning tutorial, the `adaptive.Learner1D`.
+Start with the {ref}`1D function learning tutorial<TutorialLearner1D>`.
 ```
 
 ```{include} ../../README.md

docs/source/tutorial/tutorial.Learner1D.md

@@ -9,6 +9,7 @@ jupytext:
     format_version: '0.13'
     jupytext_version: 1.13.8
 ---
+(TutorialLearner1D)=
 # Tutorial {class}`~adaptive.Learner1D`
 
 ```{note}

docs/source/tutorial/tutorial.md

@@ -17,7 +17,7 @@ evaluation.
 
 This is an introductory notebook that shows some basic use cases.
 
-We recommend to start with the {ref}`Tutorial {class}`~adaptive.Learner1D``.
+We recommend to start with the {ref}`adaptive.Learner1D tutorial<TutorialLearner1D>`.
 
 ```{note}
 Because this documentation consists of static html, the `live_plot` and `live_info` widget is not live.