Add filter to enable/disable the noscript tag added to lazyloaded images

[remyperona]

Description

Documentation

User documentation

Add a new filter rocket_lazyload_noscript with a boolean value, that can be used to enable/disable the noscript tag added to lazyloaded images.

Technical documentation

Add a new method noscriptEnabled(), and use it in the lazyloadImages and lazyloadPictures methods.

Type of change

• Enhancement (non-breaking change which improves an existing functionality).

Checklists

Feature validation

• I validated all the Acceptance Criteria. If possible, provide sreenshots or videos.
• I triggered all changed lines of code at least once without new errors/warnings/notices.
• I implemented built-in tests to cover the new/changed code.

Documentation

• I prepared the user documentation for the feature/enhancement and shared it in the PR or the GitHub issue.
• The user documentation covers new/changed entry points (endpoints, WP hooks, configuration files, ...).
• I prepared the technical documentation if needed, and shared it in the PR or the GitHub issue.

Code style

• I wrote self-explanatory code about what it does.
• I wrote comments to explain why it does it.
• I named variables and functions explicitely.
• I protected entry points against unexpected inputs.
• I did not introduce unecessary complexity.

[nicomollet]

Approved

I added an issue in rocket-lazy-load to document the new (and older) filters: wp-media/rocket-lazy-load#146