[5.3] HTTP Headers - CSP - Policy Directive: order + fancy select

[pe7er]

This PR improves the HTTP Headers system plugin under the Content Security Policy the "Policy Directive" drop down list.

Summary of Changes

The PR orders the options in the Policy Directive drop down box alphabetically and adds a fancy select layout to make it easier to find an option.

Testing Instructions

In Joomla back-end go to System > Plugins > "System - HTTP Headers" > go to the "Content-Security-Policy (CSP)" tab.
Choose for "Content Security Policy (CSP)": select "Enable", Add Directive: click the + button
Click on the Policy Directive drop down box.

Actual result BEFORE applying this Pull Request

Before the PR, the list is not ordered alphabetically.

Expected result AFTER applying this Pull Request

After applying this PR, the list is ordered alphabetically.

And the list has a fancy select layout: an extra search option to make it easier to find the right options

Link to documentations

Please select:

• Documentation link for docs.joomla.org:

• No documentation changes for docs.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed

[rachelwalraven]

I have tested this item ✅ successfully on fc78b62

Installed the fix and got the result as shown in the description.

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[Kleijson]

I have tested this item ✅ successfully on fc78b62

It works as stated

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[QuyTon]

RTC

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[laoneo]

Thanks!