include display_benchmark and benchmark_percent

also fixed some indentation

Author: zacharymnp

_docs/instructor/course_settings/rainbow_grades/customization_basics.md

@@ -43,6 +43,18 @@ It can contain the following:
    * ``"lowest_a-``, ``"lowest_b-"``, ``"lowest_c-"``, ``"lowest_d"``: Based on curves, the lowest scores that will earn
    the name of the benchmark. 
 
+  ```json
+    "display_benchmark": [
+      "average",
+      "stddev",
+      "perfect",
+      "lowest_a-",
+      "lowest_b-",
+      "lowest_c-",
+      "lowest_d"
+    ]
+  ```
+
 * **field:** ``"benchmark_percent"``  
   **type:** _associative array / mapping from string to float_  
   **REQUIRED** if using ``"curve"`` in ``"gradeables"`` described below, or if any grade-letter benchmarks are used in ``"display_benchmark"`` above.
@@ -51,6 +63,16 @@ It can contain the following:
   necessary to obtain that grade. For example to require an 82% for an A-, there should be an entry in the ``"benchmark_percent"`` array:
   ``"lowest_a-": 0.82``
 
+  To display all benchmarks, include the following:
+  ```json
+    "benchmark_percent": {
+      "lowest_a-": 0.9,
+      "lowest_b-": 0.8,
+      "lowest_c-": 0.7,
+      "lowest_d": 0.6
+    }
+  ```
+
 * **field:** ``"section"``  
   **type:** _associative array / mapping from string to string_  
   **REQUIRED**
@@ -75,16 +97,16 @@ It can contain the following:
 
   ```json
   "final_cutoff" : {
-     "A": 93.0,
-     "A-": 90.0,
-     "B+": 87.0,
-     "B": 83.0,
-     "B-": 80.0,
-     "C+": 77.0,
-     "C": 73.0,
-     "C-": 70.0,
-     "D+": 67.0,
-     "D": 63.0
+    "A": 93.0,
+    "A-": 90.0,
+    "B+": 87.0,
+    "B": 83.0,
+    "B-": 80.0,
+    "C+": 77.0,
+    "C": 73.0,
+    "C-": 70.0,
+    "D+": 67.0,
+    "D": 63.0
   }
   ```