Update links without /doc/

See cdf3755696

README.md

@@ -28,7 +28,7 @@ func main() {
 }
 ~~~
 
-Visit https://periph.io/doc/apps/samples/ for more samples.
+Show me [more samples](https://periph.io/samples/)!
 
 
 ## Authors

experimental/devices/README.md

@@ -2,4 +2,4 @@
 
 You are welcome to send PR (pull request) to add experimental device drivers
 here. Please follow the instructions in
-[doc/drivers/contributing/](https://periph.io/doc/drivers/contributing/).
+[project/contributing/](https://periph.io/project/contributing/).