Types: added Readme for npmjs to njs-types.

Author: jirutka

ts/README.md

@@ -0,0 +1,76 @@
+# TypeScript definitions for njs
+
+This package contains type definitions for [njs](https://github.com/nginx/njs) – NGINX JavaScript.
+
+
+## Usage
+
+Install **njs-types** from the [npm registry](https://www.npmjs.com/) into your project:
+
+```sh
+# using npm:
+npm install --save-dev njs-types
+# or using yarn:
+yarn add --dev njs-types
+```
+
+njs-types provides three entry points with global declarations for each of njs environments:
+
+* `njs_shell.d.ts` – njs shell
+* `ngx_http_js_module.d.ts` – NGINX JS HTTP Module
+* `ngx_stream_js_module.d.ts` – NGINX JS Stream Module
+
+You can either reference them using [triple-slash directive](https://www.typescriptlang.org/docs/handbook/triple-slash-directives.html) at top of your `.ts` files (adjust `path` to point into your project’s node_modules):
+
+```ts
+/// <reference path="./node_modules/njs-types/ngx_http_js_module.d.ts" />
+```
+
+or include them using the [files](https://www.typescriptlang.org/tsconfig#files) flag in your `tsconfig.json`, for example:
+
+```json
+{
+  "compilerOptions": {
+    "target": "ES5",
+    "module": "es2015",
+    "lib": [
+      "ES2015",
+    ],
+    "outDir": "./lib",
+    "downlevelIteration": true,
+
+    "strict": true,
+    "noImplicitAny": true,
+    "strictNullChecks": true,
+    "strictFunctionTypes": true,
+    "strictBindCallApply": true,
+    "strictPropertyInitialization": true,
+    "noImplicitThis": true,
+    "alwaysStrict": true,
+
+    "moduleResolution": "node",
+
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+  },
+  "include": [
+    "./src",
+  ],
+  "files": [
+    "./node_modules/njs-types/ngx_http_js_module.d.ts",
+  ],
+}
+```
+
+
+## Versions
+
+njs-types is typically being released together with njs.
+Their major and minor release numbers (the first two numbers) are always aligned, but the patch version (the third number) may differ.
+That's because njs-types may be updated between njs releases and in such case the patch version is incremented.
+
+It's the same strategy as used in [DefinitelyTyped](https://github.com/DefinitelyTyped/DefinitelyTyped#how-do-definitely-typed-package-versions-relate-to-versions-of-the-corresponding-library).
+The reason is that npmjs enforces [SemVer](https://semver.org/) which doesn't allow four-part version number nor provide post-release suffixes.
+
+You can find from which commit the package was built in file `COMMITHASH` inside the published package.
+It contains global revision id in the upstream repository https://hg.nginx.org/njs/ (Mercurial).