Update package to more modern standards

[Rocksheep]

Description

The package needed some more love. So I made it adhere to the max phpstan level. I already discovered some strange magic which happened on the background which could result in errors when the package was not used properly.

I have added an interface for the code to be connected to. The model must now use the Indexable interface and after that must implement it's own methods for indexation and searching of data or they can use the HasIndexation trait to add the default methods which were in the Indexable trait before.

The values in the config are now checked properly and can no longer result in errors when using wrong types. This results in having the title and content weights to actually be floats in the config. limit-results can also no longer be null. Using a limit of 0 will now result in "infinite" results.

Motivation and context

As stated I wanted to bring the package to more modern standards. There is still a lot which can be done to improve the package, but now it should be easier to do that.

How has this been tested?

I have tested this with a copy of one of the websites I worked on. I did a side by side comparison of the indexation and searching of content.

Screenshots (if appropriate)

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

Go over all the following points, and put an x in all the boxes that apply.

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