feat(examples): Introduce Ruby3.4 httpserver example

Signed-off-by: adriannnv <guzunadrian.vasile@gmail.com>

Author: adriannnv

examples/httpserver-ruby3.4/.dockerignore

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+/.unikraft/

examples/httpserver-ruby3.4/.gitignore

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+/.unikraft/

examples/httpserver-ruby3.4/Dockerfile

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+FROM unikraft.org/ruby:3.4
+
+# Simple Ruby HTTP server
+COPY ./server.rb /src/server.rb

examples/httpserver-ruby3.4/Kraftfile

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+spec: v0.6
+
+name: httpserver-ruby3.4
+
+runtime: ruby:3.4
+
+rootfs: ./Dockerfile
+
+cmd: ["/usr/bin/ruby", "/src/server.rb"]

examples/httpserver-ruby3.4/README.md

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+# Ruby Web Server
+
+This directory contains a [Ruby](https://www.ruby-lang.org/en/) web server running on Unikraft.
+
+## Set Up
+
+To run this example, [install Unikraft's companion command-line toolchain `kraft`](https://unikraft.org/docs/cli), clone this repository and `cd` into this directory.
+
+## Run and Use
+
+Use `kraft` to run the image and start a Unikraft instance:
+
+```bash
+kraft run --rm -p 8080:8080 --plat qemu --arch x86_64 -M 256M .
+```
+
+If the `--plat` argument is left out, it defaults to `qemu`.
+If the `--arch` argument is left out, it defaults to your system's CPU architecture.
+
+Once executed, it will open port `8080` and wait for connections.
+To test it, you can use `curl`:
+
+```bash
+curl localhost:8080
+```
+
+You should see a "Bye, World!" message.
+
+## Inspect and Close
+
+To list information about the Unikraft instance, use:
+
+```bash
+kraft ps
+```
+
+```text
+NAME          KERNEL                       ARGS                          CREATED         STATUS   MEM   PORTS                   PLAT
+zealous_ramu  oci://unikraft.org/ruby:3.4  /usr/bin/ruby /src/server.rb  14 minutes ago  running  244M  0.0.0.0:8080->8080/tcp  qemu/x86_64
+```
+
+The instance name is `zealous_ramu`.
+To close the Unikraft instance, close the `kraft` process (e.g., via `Ctrl+c`) or run:
+
+```bash
+kraft rm zealous_ramu
+```
+
+Note that depending on how you modify this example your instance **may** need more memory to run.
+To do so, use the `kraft run`'s `-M` flag, for example:
+
+```bash
+kraft run --rm -p 8080:8080 --plat qemu --arch x86_64 -M 512M .
+```
+
+## `kraft` and `sudo`
+
+Mixing invocations of `kraft` and `sudo` can lead to unexpected behavior.
+Read more about how to start `kraft` without `sudo` at [https://unikraft.org/sudoless](https://unikraft.org/sudoless).
+
+## Learn More
+
+- [How to run unikernels locally](https://unikraft.org/docs/cli/running)
+- [Building `Dockerfile` Images with `BuildKit`](https://unikraft.org/guides/building-dockerfile-images-with-buildkit)

examples/httpserver-ruby3.4/server.rb

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+# https://dev.to/leandronsp/web-basics-a-simple-http-server-in-ruby-2jj4
+
+require 'socket'
+
+socket = TCPServer.new(8080)
+
+loop do
+  client = socket.accept
+
+  request = client.gets
+
+  response = "HTTP/1.1 200 OK\r\n" \
+    "Content-type: text/html\r\n" \
+    "Connection: close\r\n" \
+    "\r\n" \
+    "Bye, World!"
+  client.puts(response)
+
+  client.close
+end