Change checkbox type to checkboxes in issue templates

Author: SableRaf

.github/ISSUE_TEMPLATE/1_new-library.yml

@@ -33,7 +33,7 @@ body:
     attributes:
       value: |
         Please read the [Library Guidelines](https://github.com/processing/processing4/wiki/Library-Guidelines) and make sure that your library follows them.
-  - type: checkbox
+  - type: checkboxes
     id: guidelines_confirmation
     attributes:
       label: Guidelines Confirmation

.github/ISSUE_TEMPLATE/2_new-tool.yml

@@ -33,7 +33,7 @@ body:
     attributes:
       value: |
         Please read the [Tool Guidelines](https://github.com/processing/processing/wiki/Tool-Guidelines) and make sure that your tool follows them.
-  - type: checkbox
+  - type: checkboxes
     id: guidelines_confirmation
     attributes:
       label: Guidelines Confirmation

.github/ISSUE_TEMPLATE/3_new-mode.yml

@@ -33,7 +33,7 @@ body:
     attributes:
       value: |
         Please read the [Mode Overview](https://github.com/processing/processing/wiki/Mode-Overview) and make sure that your mode follows the guidelines.
-  - type: checkbox
+  - type: checkboxes
     id: guidelines_confirmation
     attributes:
       label: Guidelines Confirmation

.github/ISSUE_TEMPLATE/4_new-examples.yml

@@ -33,7 +33,7 @@ body:
     attributes:
       value: |
         Please read the [Examples Overview](https://github.com/processing/processing/wiki/Examples-Overview) and make sure that your example pack follows the guidelines.
-  - type: checkbox
+  - type: checkboxes
     id: guidelines_confirmation
     attributes:
       label: Guidelines Confirmation