Add php_phpactor_executable for phpactor and make it configurable
through php_phpactor_config.
When phpactor was first added in 3b8ff65, it had no configuration. Thus
the documentation for it could be completely blank. That is why it now
seems like an initial addition
Co-authored-by: cos <cos>
* Adds phpactor lsp linter
* Fixes missing comma
* Adds tests for phpactor lsp linter
* Adds note that this part is not my own work
* Removes unused variable
* Adds phpactor to supported tools list
* Fixes doc sorting
* Wraps phpactor in code tags