Add Dependencies Checking Command

[dan-tang-ssd]

This PR is submitted to add dependencies checking command.

It is submitted to show the required program changes. It is more desirable to prepare this feature in a separate package.
Therefore, this PR is submitted for code review rather than merging it into dev branch.

---

It contains below changes:

• develop a command program to run command "composer audit", send the execution result to pre-defined multiple email addresses
• get pre-defined multiple email addresses from config item in .env file, tokenise it as it may contain multiple email addresses
• put "composer audit" execution result as a tabular data in email template. Use PRE tag to show all whitespaces in the result string
• set font to fixed width font "Courier New", to show execution result as tabular data properly

Originally I planned to run this command as schedule job. Considering there are different ways to run schedule job in different Laravel version. I will leave it to the application developer.

---

Screen shots: