add example input/outputs to starlark examples

plugins/processors/starlark/testdata/number_logic.star

@@ -1,4 +1,11 @@
-# Set  any 'status' field between 1 and 6 to a value of 0
+# Set a logic function to transform a numerical value to another numerical value
+# Example: Set  any 'status' field between 1 and 6 to a value of 0
+#
+# Example Input:
+# lb, http_method=GET status=5 1465839830100400201
+# Example Output:
+# lb, http_method=GET status=0 1465839830100400201
+
 
 def apply(metric):
     v = metric.fields.get('status')

plugins/processors/starlark/testdata/ratio.star

@@ -1,4 +1,11 @@
 # Compute the ratio of two integer fields.
+#
+# Example: A new field 'usage' from an existing fields 'used' and 'total'
+#
+# Example Input:
+# memory, host=hostname used=11038756864.4948,total=17179869184.1221 1597255082000000000
+# Example Output:
+# memory, host=hostname used=11038756864.4948,total=17179869184.1221,usage=64.254021647 1597255082000000000
 
 def apply(metric):
     used = float(metric.fields['used'])

plugins/processors/starlark/testdata/rename.star

@@ -1,4 +1,9 @@
 # Rename any tags using the mapping in the renames dict.
+#
+# Example Input:
+# measurement, host=hostname lower=0,upper=100 1597255410000000000
+# Example Output:
+# measurement, host=hostname min=0,max=100 1597255410000000000
 
 renames = {
     'lower': 'min',

plugins/processors/starlark/testdata/scale.star

@@ -1,4 +1,9 @@
 # Multiply any float fields by 10
+#
+# Example Input:
+# modbus,host=hostname Current=1.22,Energy=0,Frequency=60i,Power=0,Voltage=123.9000015258789 1554079521000000000
+# Example Output:
+# modbus,host=hostname Current=12.2,Energy=0,Frequency=60i,Power=0,Voltage=1239.000015258789 1554079521000000000
 
 def apply(metric):
     for k, v in metric.fields.items():