Add schema validation for collection files #369

This commit improves collection file editing and error detection
directly in the IDE. It adds YAML schema, IDE configuration and
automatic tests to validate it.

- Introduce a YAML schema for collection file.
- Use `yaml-language-server` for enhanced YAML support in VSCode.
- Add telemetry disabling in `configure_vscode.py` to respect user
  privacy.
- Add automated checks to validate YAML file structure against the
  schema.
- Remove unused properties and do not allow them in compiler.

src/application/collections/collection.yaml.d.ts

@@ -16,7 +16,7 @@ declare module '@/application/collections/*' {
   }
 
   export type ExecutableData = CategoryData | ScriptData;
-  export type DocumentationData = ReadonlyArray<string> | string | undefined;
+  export type DocumentationData = ReadonlyArray<string> | string;
 
   export interface DocumentableData {
     readonly docs?: DocumentationData;
@@ -73,7 +73,6 @@ declare module '@/application/collections/*' {
 
   export interface ScriptingDefinitionData {
     readonly language: string;
-    readonly fileExtension: string;
     readonly startCode: string;
     readonly endCode: string;
   }