Added documentation on findent

Documentation now includes the options for findent which reproduce the
target formatting.

doc/pages/code-style.md

@@ -36,6 +36,14 @@ end module example
 
 Please note that the maximum line length in Neko should not exceed 80 columns.
 
+Additionally the [findent](https://github.com/wvermin/findent) tool can be used
+to enforce these rules by assigning the following options.
+
+```sh
+findent -i2 -d3 -f3 -s3 -w3 -t3 -j3 -k- -Rr -c3 < input.f90 > formatted.f90
+```
+
+
 ## Data types
 For portability reasons, it is essential to only use data type kinds defined in num_types.f90 and avoid legacy constructs like `real*8` or `integer(kind=8)`