Adds PHPActor Linter (LSP) (#3975)

* 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

ale_linters/php/phpactor.vim

@@ -0,0 +1,23 @@
+" Author: Arizard <https://github.com/Arizard>
+" Description: PHPactor integration for ALE
+
+" Copied from langserver.vim
+function! ale_linters#php#phpactor#GetProjectRoot(buffer) abort
+    let l:composer_path = ale#path#FindNearestFile(a:buffer, 'composer.json')
+
+    if (!empty(l:composer_path))
+        return fnamemodify(l:composer_path, ':h')
+    endif
+
+    let l:git_path = ale#path#FindNearestDirectory(a:buffer, '.git')
+
+    return !empty(l:git_path) ? fnamemodify(l:git_path, ':h:h') : ''
+endfunction
+
+call ale#linter#Define('php', {
+\   'name': 'phpactor',
+\   'lsp': 'stdio',
+\   'executable': 'phpactor',
+\   'command': '%e language-server',
+\   'project_root': function('ale_linters#php#phpactor#GetProjectRoot'),
+\})