Add event calendar and update site content

Add a calendar page and ICS file for event subscriptions. Update the
Hello Linux presentation with Tux images and add setup instructions
to the README.

README.md

@@ -2,22 +2,26 @@
 
 This repository contains the FLUG presentations.
 
-## Serving localls
+## Usage
+
+Install the required dependencies:
 
-Run once to install Vite globally:
 ```bash
-npm install -g vite
+nvm use stable
 npm install
+npm install -g vite
 ```
 
 Run the development server:
+
 ```bash
-vite serve
+vite
 ```
 
 ## Building docker image
 
 To build the Docker image, run:
+
 ```bash
 docker buildx build --platform linux/arm64 --push -t docker.tipsy.codes/flug:20260519 .
 ```