chore(build): automate build process (#33)

TL;DR: `npm run release` creates new releases.

incorporate release-it (https://www.npmjs.com/package/release-it) to
manage our builds, github tagging and github releases.

**creating a build**
Run `npm run release`: this will kick-off the `release.sh` script. It
expects a `GITHUB_TOKEN` located at a local `.env` file. Then, it runs
`npm install` and `npm run test`. If they succeed, then it proceeds to
create a new build by running `npm run build`.
Lastly, you will see an interactive CLI interface, where you can select
`patch`, `minor` or `major` among the options.

The result is a new git tag with the corresponding version, and a new
Github release.

Author: elfrank

.gitignore

@@ -2,6 +2,9 @@
 
 node_modules
 
+# file with envinronment variables
+.env
+
 # demo/test scenes
 demos/
 test-scene/

.release-it.json

@@ -0,0 +1,50 @@
+{
+  "hooks": {
+    "before:init": ["npm install", "npm run test"],
+    "after:bump": "npm run build",
+    "after:release": "echo Successfully released ${name} v${version} to ${repo.repository}."
+  },
+  "git": {
+    "changelog": "git log --pretty=format:\"* %s (%h)\" ${latestTag}...HEAD",
+    "requireCleanWorkingDir": true,
+    "requireUpstream": true,
+    "requireCommits": false,
+    "addUntrackedFiles": false,
+    "commit": true,
+    "commitMessage": "Release ${version}",
+    "commitArgs": "",
+    "tag": true,
+    "tagName": "${version}",
+    "tagAnnotation": "Release ${version}",
+    "tagArgs": "",
+    "push": true,
+    "pushArgs": "--follow-tags",
+    "pushRepo": "origin"
+  },
+  "npm": {
+    "publish": false,
+    "publishPath": ".",
+    "access": null,
+    "otp": null
+  },
+  "github": {
+    "release": true,
+    "releaseName": "Release v${version}",
+    "releaseNotes": null,
+    "preRelease": false,
+    "draft": false,
+    "tokenRef": "GITHUB_TOKEN",
+    "assets": null,
+    "host": null,
+    "timeout": 0,
+    "proxy": null
+  },
+  "gitlab": {
+    "release": false,
+    "releaseName": "Release ${version}",
+    "releaseNotes": null,
+    "tokenRef": "GITLAB_TOKEN",
+    "assets": null,
+    "origin": null
+  }
+}