Add type definition for error-subclass (#27811)

types/error-subclass/error-subclass-tests.ts

@@ -0,0 +1,7 @@
+import ErrorSubclass from 'error-subclass';
+
+class ExampleError extends ErrorSubclass {
+    static displayName = 'ExampleError';
+}
+
+throw new ExampleError('Something went wrong!');

types/error-subclass/index.d.ts

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+// Type definitions for error-subclass 2.2
+// Project: https://github.com/spudly/error-subclass#readme
+// Definitions by: Fitbit <https://github.com/fitbit>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+export default class ErrorSubclass extends Error {
+    static displayName: string;
+}

types/error-subclass/tsconfig.json

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+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "lib": [
+            "es6"
+        ],
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictNullChecks": true,
+        "baseUrl": "../",
+        "typeRoots": [
+            "../"
+        ],
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true,
+        "strictFunctionTypes": true
+    },
+    "files": [
+        "index.d.ts",
+        "error-subclass-tests.ts"
+    ]
+}

types/error-subclass/tslint.json

@@ -0,0 +1 @@
+{ "extends": "dtslint/dt.json" }