Fixed codechecker problems and added two new settings for EnlighterJS

[cli-ish]

This PR contains:

• Codechecker fixes
• php Type declarations which are possible since the 7.4 version of php (where it was possible)
• 2 new Settings enlighterjsselector1 and enlighterjsselector2 which allow the control over which tags should be used.
• fixed up the test cases + coverage.

If there are any question dont mind to ask :)

[gjb2048]

Dear @cli-ish,

There are so many things wrong with the changes you're proposing, I almost don't know where to begin, right:

• You've broken the correct indentation.
• You've corrected my style of English, and yet I am British!
• You've corrected the copyright.
• You've broken my version number policy.
• You've added PHP language features that won't be supported in the PHP versions for M3.7 etc.
• You've corrected '// stylelint-disable-line declaration-no-important' in the CSS but you don't know that the preprocessor removes this and its only there for 'stylelint', now with '/*' style comments then it will actually end up in the output!
• You've deleted the 'codeexample' default and yet clearly didn't rerun the PHP unit tests, as they could have to change.
• You've corrected the way I've imported the toolbox in filter.php - pointless.
• With the 'enlighterjsselector1' and 'enlighterjsselector2' settings you've allowed the 'synhi' part to be changed and yet that's fixed within the 'filter.php' file and should not be changed causing user frustration if they accidentally break this.
• You've changed all of the indentation and broken some of the spacing in my Readme.md file!

As I'm sure you can now realise, I'm rejecting this! If you submit a patch, please keep it specific to the problem you believe exists, clearly demonstrating what the problem is and why you are solving it.

[gjb2048]

P.S. If you think I'm being harsh, then I'm not. Attempt to do the same thing with Moodle core code in the Tracker and you'll get the same response. You have to stick to changes that relate directly to the problem. Correcting the style of other people's code is not allowed.

And, additionally, why? Why are you doing this? Why are you spending time on this?