Document keys and values modifiers (#1352)

Author: duncanmcclean

content/collections/modifiers/keys.md

@@ -0,0 +1,30 @@
+---
+id: 9197be05-5e2d-400f-a0f0-c52a4d460e60
+blueprint: modifiers
+title: Keys
+modifier_types:
+  - array
+  - utility
+---
+Retrieves just the keys from the given array.
+
+```yaml
+the_team:
+    jack: Jack McDade
+    jason: Jason Varga
+    jesse: Jesse Leite
+    joshua: Joshua Blum
+    duncan: Duncan McClean
+```
+
+```
+{{ the_team | keys }}
+```
+
+```yaml
+- jack
+- jason
+- jesse
+- joshua
+- duncan
+```

content/collections/modifiers/values.md

@@ -0,0 +1,30 @@
+---
+id: b57caa5c-ae9e-4220-b8a6-f7c82d16f0df
+blueprint: modifiers
+title: Values
+modifier_types:
+  - array
+  - utility
+---
+Retrieves just the keys from the given array.
+
+```yaml
+the_team:
+    jack: Jack McDade
+    jason: Jason Varga
+    jesse: Jesse Leite
+    joshua: Joshua Blum
+    duncan: Duncan McClean
+```
+
+```
+{{ the_team | values }}
+```
+
+```yaml
+- Jack McDade
+- Jason Varga
+- Jesse Leite
+- Joshua Blum
+- Duncan McClean
+```