chore: add npm version script (#1474)

* chore: add npm version script

* docs(CONTRIBUTING): update Releasing new versions section

Add a note that these instructions concern NativeScript Core Team Members.

* docs(CONTRIBUTING): address comments

Author: vchimev

CONTRIBUTING.md

@@ -11,6 +11,7 @@ Here are some guides on how to do that:
 - [Requesting Features](#requesting-features)
 - [Submitting a PR](#submitting-a-pr)
 - [Where to Start](#where-to-start)
+- [Publishing new versions](#publishing-new-versions)
 
 <!-- /TOC -->
 
@@ -76,3 +77,40 @@ It's our turn from there on! We will review the PR and discuss changes you might
 ## Where to Start
 
 If you want to contribute, but you are not sure where to start - look for [issues labeled `help wanted`](https://github.com/NativeScript/nativescript-angular/issues?q=is%3Aopen+is%3Aissue+label%3A%22help+wanted%22).
+
+
+## Publishing new versions
+
+Instructions how to publish a new version for Maintainers.
+
+1. Execute `npm install` to install dependencies and prepare the package for publishing:
+```bash
+cd nativescript-angular/nativescript-angular
+npm install
+```
+
+2. Add the following to your `.npmrc`:
+```
+tag-version-prefix=""
+message="release: cut the %s release"
+```
+
+3. Create new branch for the release:
+```bash
+git checkout -b username/release-version
+```
+
+4. Execute [`npm version`](https://docs.npmjs.com/cli/version) to bump the version in the `package.json` file, tag the release and update the CHANGELOG.md:
+```bash
+npm version [patch|minor|major]
+```
+
+5. Push all the changes to your branch and create a pull request:
+```bash
+git push --set-upstream origin username/release-version --tags
+```
+
+6. Publish the package to `npm` after the pull request is merged:
+```bash
+npm publish
+```

nativescript-angular/package.json

@@ -33,7 +33,8 @@
     "tsc": "tsc -p tsconfig.json",
     "tsc-w": "tsc -p tsconfig.json -w",
     "ngc": "ngc -p tsconfig.json",
-    "prepare": "npm run ngc"
+    "prepare": "npm run ngc",
+    "version": "rm package-lock.json && conventional-changelog -p angular -i ../CHANGELOG.md -s && git add ../CHANGELOG.md"
   },
   "bin": {
     "update-app-ng-deps": "./bin/update-app-ng-deps"