Update resolver in stack.yaml

- Resolver was outdated and thus the project could not be built with
`stack build`. Now it matches the current packages version bounds
specified in cabal project config.

Author: AleXoundOS

stack.yaml

@@ -15,7 +15,7 @@
 # resolver:
 #  name: custom-snapshot
 #  location: "./custom-snapshot.yaml"
-resolver: lts-9.6
+resolver: lts-13.17
 
 # User packages to be built.
 # Various formats can be used as shown in the example below.
@@ -63,4 +63,4 @@ extra-package-dbs: []
 # extra-lib-dirs: [/path/to/dir]
 #
 # Allow a newer minor version of GHC than the snapshot specifies
-# compiler-check: newer-minor
+# compiler-check: newer-minor