refactor: migrate to ruby:2.7 for Dockerfile

Dockerfile

@@ -1,4 +1,4 @@
-FROM ruby:2.7-slim
+FROM ruby:2.7
 
 LABEL version="0.1.0"
 LABEL repository="https://github.com/jeffreytse/jekyll-deploy-action"
@@ -8,19 +8,17 @@ LABEL maintainer="Jeffrey Tse <jeffreytse.mail@gmail.com>"
 # Update packages database
 RUN apt-get update
 
-RUN apt-get install -qq -y git-all build-essential
+# Installing git package
+RUN apt-get install -qq -y git-all
 
 # Allow for timezone setting in _config.yml
 RUN apt-get install -qq -y tzdata
 
 # Installing imagemagick library
 RUN apt-get install -qq -y pkg-config libmagick++-dev
 
-# Installing gsl library for gsl
-RUN apt-get install -qq -y libgsl-dev
-
-# Installing atlas library for nmatrix
-RUN apt-get install -qq -y libatlas-base-dev
+# Installing gsl and atlas libraries
+RUN apt-get install -qq -y libgsl-dev libatlas-base-dev
 
 # debug
 RUN bundle version