about: fix webpage type

content/page/about.md

@@ -57,7 +57,7 @@ Below is the planned timeline of the course. The specific contents of each sessi
 
 Särkkä, S. (2013). **Bayesian Filtering and Smoothing** (Institute of Mathematical Statistics Textbooks). Cambridge: Cambridge University Press. doi:10.1017/CBO9781139344203
 
-More details on the [author's webapge](https://users.aalto.fi/~ssarkka/#publications)
+More details on the [author's webpage](https://users.aalto.fi/~ssarkka/#publications)
 
 ### Other readings