kyaml: refactor command documentation into .md files from go files

No new documentation added.

cmd/config/docs/commands/run-fns.md

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+## run-fns
+
+Apply config functions to Resources.
+
+### Synopsis
+
+Apply config functions to Resources.
+
+run-fns sequentially invokes all config functions in the directly, providing Resources
+in the directory as input to the first function, and writing the output of the last
+function back to the directory.
+
+The ordering of functions is determined by the order they are encountered when walking the
+directory.  To clearly specify an ordering of functions, multiple functions may be
+declared in the same file, separated by '---' (the functions will be invoked in the
+order they appear in the file).
+
+#### Arguments:
+
+  DIR:
+    Path to local directory.
+
+#### Config Functions:
+
+  Config functions are specified as Kubernetes types containing a metadata.configFn.container.image
+  field.  This fields tells run-fns how to invoke the container.
+
+  Example config function:
+
+	# in file example/fn.yaml
+	apiVersion: fn.example.com/v1beta1
+	kind: ExampleFunctionKind
+	metadata:
+	  configFn:
+	    container:
+	      # function is invoked as a container running this image
+	      image: gcr.io/example/examplefunction:v1.0.1
+	  annotations:
+	    config.kubernetes.io/local-config: "true" # tools should ignore this
+	spec:
+	  configField: configValue
+
+  In the preceding example, 'kyaml run-fns example/' would identify the function by
+  the metadata.configFn field.  It would then write all Resources in the directory to
+  a container stdin (running the gcr.io/example/examplefunction:v1.0.1 image).  It
+  would then writer the container stdout back to example/, replacing the directory
+  file contents.
+
+  See `kyaml help docs-fn` for more details on writing functions.
+
+### Examples
+
+kyaml run-fns example/