Add script to install and run shellcheck and tweak shellcheckrc

Run a script to install and run pre-commit in a python3 virtual environment and
tweak shellcheckrc to allow the venv activation source as part of the script.

shellcheck...............................................................Passed

Author: steve-downey

.shellcheckrc

@@ -1,3 +1,4 @@
 # shellcheck
 # allow for non-alphanumeric filenames
 disable=SC2038
+external-sources=true

scripts/install_run_precommit.sh

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+
+python3 -m venv .venv
+
+. .venv/bin/activate && python3 -m pip install --upgrade pip setuptools wheel
+. .venv/bin/activate && python3 -m pip install pip-tools
+. .venv/bin/activate && python3 -m piptools sync requirements.txt
+. .venv/bin/activate && python3 -m piptools sync requirements-dev.txt
+. .venv/bin/activate && pre-commit run -a