EPIC Validation of alt text on save

Problem/Motivation

This is the epic to cover the addition of the Validation of Alt Text

Issues in the epic (in order)

• MVP
• #3495154: Add admin route for admin form
• #3495155: Add menu item for admin form
• #3502101: Alter on off switch on module admin form
• #3495141: Add custom field for alt text validation rules to settings form
• #3502105: Add global response headings to admin settings
• #3505126: Create default settings yml for config install
• #3495175: Add validator that applies all the rules
• #3495176: Add validation rule case for for rule type: Cannot exceed length
• #3495185: Add validation rule case: Can not match image filename
• #3499555: Add validation rule case for Cannot match image title
• #3534376: Implement the design for Rule add/edit
• Post MVP
• #3495187: Add client side validation of all validations
• Abandoned
• #3495183: Add optional check for filename to admin form
• #3495178: Add length limit to admin form