Support PHP8 attributes

Attributes instead of annotations can now be used. Both are supported on PHP8.

Better support typed properties

Also removes compatibility to diverging property paths defined
in the form, we only support direct properties which are
mapped 1:1 in the form. This seems easiest and anything else
would just lead to a headache, although maybe there is a better
option sometime in the future or when we go PHP 8 only.

Note that if filter annotations are used without direct mappings,
this might lead to errors and/or not work anymore.

The PHP 8 support is preliminary, as it was not tested yet.

v0.8.6

Relax PHP version constraint

Add RemoveHTMLTagCharacters filter

Removes <, > and ".

v0.8.4: Make library PHP 7.4+ only

- Use new functionality as far as possible
- Improve project configuration

v0.8.3

Allow Symfony 5 and switch to composer-bin-plugin

v0.8.2: Add string testers to component

These test a string according to a certain criteria and
return either true or false.

The goal is to have some commonly useful testers in
this component. So far we just have the valid UTF8
and the valid datetime testers, but additional testers
for things like IPs, domains, emails etc. could be
helpful too. Some of the string filters could be adapted
to have a tester version, for when you just want to find
out if a string is valid not forceably change it.

v0.8.1

Add property path checks with forms

Major improvements to documentation & filters

• Add documentation for all filters
• Refine many filters to be more unicode compatible, cover more use cases, or be more efficient (less regex)
• Adjusts tests to remain at 100% coverage

v0.7.1: Improve NormalizeLettersToAscii & add new filters

- Make very intense tests about the characters which should
  be converted in NormalizeLettersToAsciiFilter and add many
  additional conversions to have better and more complete
  results
- Add RemoveEmailsFilter and RemoveURLsFilter
- Rename the "Manager" tests to "Selector" tests to be consistent