[exercises] Update README

Author: woojiahao

README.md

@@ -15,13 +15,13 @@ Configuration fields for each exercise:
 4. `requires_github`: downloading the exercise will check that Github and Github CLI is installed
 5. `base_files`: provides the files to be included outside of the repository, along with `.gitmastery-exercise.json` and `README.md`, most often used for `answers.txt`
 6. `exercise_repo`: configuration for what the exercise repository would look like
-    1. `type`: `custom` (creates and initializes the folder as a Git repository) or `link` (reference a repository on Github)
-    2. `name`: name of repository during cloning
-    3. `link`: (only read if `link` is present) link of repository on Github
+    1. `repo_type`: `local` (creates and initializes the folder as a Git repository) or `remote` (reference a repository on Github)
+    2. `repo_name`: name of repository during cloning
+    3. `repo_title`: (only read if `link` is present) link of repository on Github
     4. `create_fork`: (only read if `link` is present) flag to determine if we need to fork the repository to the student's machine, otherwise it just clones the repository
     5. `init`: (only read if `custom` is present) flag to determine if we will call `git init` on the exercise repository (useful if we don't want to start out with a Git repository)
 
 
 ## TODOs
 
-- [ ] Add validation for exercise configuration (e.g. cannot fork + not require Github) - to run as CI
+- [X] Add validation for exercise configuration (e.g. cannot fork + not require Github) - to run as CI