Fix measure link
<a href="/extract">extract</a><br>
<a href="/filter">filter</a><br>
<a href="/materialize">materialize</a><br>
- <a href="/merge">measure</a><br>
+ <a href="/measure">measure</a><br>
<a href="/merge">merge</a><br>
<a href="/mirror">mirror</a><br>
<a href="/python">python</a><br>
