Disallow a difficulty level of 0

Author: ee7

building/configlet/lint.md

@@ -144,7 +144,7 @@ The `config.json` file should have the following checks:
 - The `"exercises.practice[].uuid"` value must be a unique version 4 UUID string⁵
 - The `"exercises.practice[].uuid"` value for each exercise must never change
 - The `"exercises.practice[].difficulty"` key is required
-- The `"exercises.practice[].difficulty"` value must be an integer >= 0 and <= 10
+- The `"exercises.practice[].difficulty"` value must be an integer >= 1 and <= 10
 - The `"exercises.practice[].practices"` key is required
 - The `"exercises.practice[].practices"` value must be a non-empty array of strings if `"exercises.practice[].status"` is not equal to `deprecated`
 - The `"exercises.practice[].practices"` value must be an empty array if `"exercises.practice[].status"` is equal to `deprecated`

building/tracks/config-json.md

@@ -147,7 +147,7 @@ Each concept exercise is an entry in the `exercises.practice` array. The followi
 - `name`: the exercise's name. Its length must be <= 255.
 - `practices`: an array of concept slugs that the exercise is helping students practice
 - `prerequisites`: an array of concept slugs that must be unlocked before a student can start the exercise
-- `difficulty`: a number indicating the difficulty of the exercise. The number must be in the range of 0 (easiest) to 10 (hardest). The website interprets the difficulty as follows:
+- `difficulty`: a number indicating the difficulty of the exercise. The number must be in the range of 1 (easiest) to 10 (hardest). The website interprets the difficulty as follows:
   - 1,2,3: easy
   - 4,5,6,7: medium
   - else: hard