Add rvmrc to docs

docs/.rvmrc

@@ -0,0 +1,60 @@
+#!/usr/bin/env bash
+
+# This is an RVM Project .rvmrc file, used to automatically load the ruby
+# development environment upon cd'ing into the directory
+
+# First we specify our desired <ruby>[@<gemset>], the @gemset name is optional,
+# Only full ruby name is supported here, for short names use:
+#     echo "rvm use 3.0.0@braidpoolblog" > .rvmrc
+environment_id="ruby-3.0.0@braidpoolblog"
+
+# Uncomment the following lines if you want to verify rvm version per project
+# rvmrc_rvm_version="1.29.12 (latest)" # 1.10.1 seems like a safe start
+# eval "$(echo ${rvm_version}.${rvmrc_rvm_version} | awk -F. '{print "[[ "$1*65536+$2*256+$3" -ge "$4*65536+$5*256+$6" ]]"}' )" || {
+#   echo "This .rvmrc file requires at least RVM ${rvmrc_rvm_version}, aborting loading."
+#   exit 1
+# }
+
+# First we attempt to load the desired environment directly from the environment
+# file. This is very fast and efficient compared to running through the entire
+# CLI and selector. If you want feedback on which environment was used then
+# insert the word 'use' after --create as this triggers verbose mode.
+if [[ -d "${rvm_path:-$HOME/.rvm}/environments"
+  && -s "${rvm_path:-$HOME/.rvm}/environments/$environment_id" ]]
+then
+  \. "${rvm_path:-$HOME/.rvm}/environments/$environment_id"
+  for __hook in "${rvm_path:-$HOME/.rvm}/hooks/after_use"*
+  do
+    if [[ -f "${__hook}" && -x "${__hook}" && -s "${__hook}" ]]
+    then \. "${__hook}" || true
+    fi
+  done
+  unset __hook
+  if (( ${rvm_use_flag:=1} >= 1 )) # display automatically
+  then
+    if [[ $- == *i* ]] # check for interactive shells
+    then printf "%b" "Using: $(tput setaf 2 2>/dev/null)$GEM_HOME$(tput sgr0 2>/dev/null)\n" # show the user the ruby and gemset they are using in green
+    else printf "%b" "Using: $GEM_HOME\n" # don't use colors in non-interactive shells
+    fi
+  fi
+else
+  # If the environment file has not yet been created, use the RVM CLI to select.
+  rvm --create use  "$environment_id" || {
+    echo "Failed to create RVM environment '${environment_id}'."
+    return 1
+  }
+fi
+
+# If you use bundler, this might be useful to you:
+# if [[ -s Gemfile ]] && {
+#   ! builtin command -v bundle >/dev/null ||
+#   builtin command -v bundle | GREP_OPTIONS="" \command \grep $rvm_path/bin/bundle >/dev/null
+# }
+# then
+#   printf "%b" "The rubygem 'bundler' is not installed. Installing it now.\n"
+#   gem install bundler
+# fi
+# if [[ -s Gemfile ]] && builtin command -v bundle >/dev/null
+# then
+#   bundle install | GREP_OPTIONS="" \command \grep -vE '^Using|Your bundle is complete'
+# fi