Please include envsubst and pcregrep in convenience images

[jasonkuhrt]

The pre-built convenience images provided by circleci are a great help. They also ship with some standard tooling that is of great help when dropping down to bash. For example

❯ docker run --rm circleci/python:3.7 jq --version
jq-1.6

There are two tools that I have found essential after writing a half dozen orbs that I would kindly request be considered for bundling into the convenience images:

• envsubst
• pcregrep

[drazisil]

Thanks for the suggestion, Jason. I’ve passed this along to the team that builds the images.