Add ruby dev for pg gem (#3)

* Mods Dockerfile to use ruby 3.3.6 in the hopes this allows us to use ruby-dev, required by 'pg' gem.

* Add a few apk packages so that this image can work for any ruby apps that need the pg gem

Author: devjona

Dockerfile

@@ -1,13 +1,16 @@
 # About APK: https://wiki.alpinelinux.org/wiki/Alpine_Package_Keeper
 # Packages are here: https://pkgs.alpinelinux.org/packages
 
-FROM alpine:3.20
+FROM alpine:3.21
 
 # Install Ruby and necessary dependencies:
 # irb wouldn't run because rdoc was missing
 
-RUN apk add --clean ruby=3.3.3-r0 \
-  vim && \
+RUN apk add --clean ruby \
+  vim \
+  ruby-dev \
+  build-base \
+  postgresql-dev && \
   gem install rdoc && \
   gem install bundler