Automate URL and typo checking when README.md is checked in

[petefoth]

We should implement some tests / checks to be run when README.md is run.

The following comment has details of how to check for incorrect URLs, and for 'space before comma' typos

Possible tests

I have not used the Markdown editor MarkText for this commit (hence #499), but with its spell checker (on Linux Mint in my case) already raises some typos such as:

• buid
• intallation
• knowlegdeable

In addition to find out incorrect commas use:

grep -E " ,|,'" README.md

I just established (hence #499) the following command-line to check URL updates:

grep -Eo "(http|https)://[a-zA-Z0-9./?=_%:-]*" README.md | sort -u | xargs -i sh -c 'curl -s -I "{}" | grep -wq "301" && echo "{}" && curl -s -I "{}" | grep location | cut -d ':' -f2-'> ```


currently outputting:

https://source.android.com/setup/build/building
/docs/setup/build/building

The tests should be implemented in a new workflow README-check.yml