[negative-index] Add types (#63239)

types/negative-index/index.d.ts

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+// Type definitions for negative-index 1.0
+// Project: https://github.com/dy/negative-index#readme
+// Definitions by: BendingBender <https://github.com/BendingBender>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+export = negativeIndex;
+
+/**
+ * Convert negative index to positive starting from the end. Same way
+ * [Array.slice](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/slice)
+ * arguments work.
+ *
+ * @example
+ * import idx = require('negative-index');
+ *
+ * idx(-5, 8); // 3
+ * idx(5, 8); // 5
+ *
+ * @example
+ * // Works well for normalizing real numbers offset, like time etc:
+ *
+ * import normOffset = require('negative-index');
+ *
+ * const time = -.15, duration = 2.45;
+ *
+ * normOffset(time, duration); // 2.3
+ */
+declare function negativeIndex(index: number, length: number): number;

types/negative-index/negative-index-tests.ts

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+import idx = require('negative-index');
+
+idx(5, 8); // $ExpectType number

types/negative-index/tsconfig.json

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

types/negative-index/tslint.json

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+{ "extends": "@definitelytyped/dtslint/dt.json" }