add ruby demo (#53)

## Summary

Added a simple Ruby demo along with the corresponding Dockerfile and
deployment.yaml. The Ruby code performs nested function calls and checks
the first 1000 numbers for primes. It's a simple and effective way to
give the CPU a bit of work.

---------

Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>

Author: marcosdotps

ruby/Dockerfile

@@ -0,0 +1,5 @@
+FROM ruby:bullseye
+
+COPY ./app.rb /tmp
+
+CMD ["ruby", "/tmp/app.rb"]

ruby/Makefile

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+.PHONY: build
+build:
+	docker build -t parca-demo:ruby .

ruby/app.rb

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+require 'prime'
+require 'fileutils'
+
+STDOUT.sync = true
+
+def a(n)
+    b(n)
+end
+
+def b(n)
+    ## Make some calculations
+    i = 100_000
+    while i > 0 do
+        Prime.prime?(i)
+        i -= 1
+    end
+    c(n)
+end
+
+def c(n)
+    ## Create a new file
+    File.open("test.txt", "w") do |f|
+        f.write("Hello, world!")
+    end
+    ## Pass new file to d
+    d("test.txt")
+end
+
+def d(file)
+    ## Read file
+    File.open(file, "r") do |f|
+        ## Print file contents and time
+        puts f.read + " :: " + Time.now.to_s
+    end
+    f(file)
+end
+
+def f(file)
+    ## Delete file
+    File.delete(file)
+end
+
+## Infinte loop
+while true
+    sleep(1)
+    a(1)
+end

ruby/deployment.yaml

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+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  labels:
+    app.kubernetes.io/name: demo-ruby
+  name: ruby
+  namespace: parca
+spec:
+  replicas: 3
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: demo-ruby
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/name: demo-ruby
+    spec:
+      containers:
+      - image: parca-demo:ruby
+        name: python
+        resources:
+          limits:
+            cpu: "100m"
+            memory: "256Mi"