Update README.md

Author: jonasjabari

docs/start/100-installation/README.md

@@ -1,13 +1,13 @@
-# Installation guide
+# Installation/Update guide
 
-This guide shows you how to add the `matestack-ui-core` gem to an existing Rails application.
+This guide shows you how to add the `matestack-ui-core` gem to an existing Rails application and update it.
 
 ## Installation
 
 Add 'matestack-ui-core' to your Gemfile
 
 ```ruby
-gem 'matestack-ui-core', '~> 1.2'
+gem 'matestack-ui-core', '~> 1.3'
 ```
 
 and run
@@ -44,3 +44,57 @@ end
 Now, you are able to create UI components in pure Ruby and use them in your Rails views. Additionally you can substitute Rails views and layouts with Matestack pages and apps.
 
 If you want to use Matestack's optional reactivity features in pure Ruby (through dynamic Vue.js components such as `form` and `async` or dynamic page transitions), please follow this [guide](/docs/reactive_components/100-rails_integration/) to set up the JavaScript parts via AssetPipeline or Webpacker.
+
+## Update
+
+### Ruby Gem
+
+Depending on the entry in your Gemfile, you might need to adjust the allowed version ranges in order to update the Gem. After checked and adjusted the version ranges, run:
+
+```bash
+bundle update matestack-ui-core
+```
+
+and then check the installed version:
+
+```bash
+bundle info matestack-ui-core
+```
+
+### JavaScript via AssetPipeline/Sprockets
+
+If you've installed the JavaScript dependecies via AssetPipeline/Sprockets, updating the Ruby gem is enough! Nothing to do here!
+
+### JavaScript via Yarn
+
+If you've installed the JavaScript dependecies via Yarn/Webpacker you need to update the JavaScript assets manually:
+
+In your package.json, change the version number used in the GitHub path referencing the repo of `matestack-ui-core`. This version number have to match the currently installe version of the Ruby Gem of `matestack-ui-core`
+
+`package.json`
+
+```json
+{
+  "name": "xyz",
+  "dependencies": {
+    // adjust the following path in order to match the Ruby Gem version!
+    "matestack-ui-core": "https://github.com/matestack/matestack-ui-core#v1.3.0", 
+  }
+}
+
+```
+
+and then run:
+
+```bash
+yarn install
+```
+
+and finally check if the correct version is installed:
+
+```bash
+yarn list --pattern "matestack-ui-core"
+```
+
+
+