Use location of composer.json for PHP project path too (#2391)

* move php-langserver "test for .git dir" test-project to its own directory
* search for composer.json file in php-langserver first then .git dir
* add test for php-langserver composer.json

ale_linters/php/langserver.vim

@@ -5,6 +5,12 @@ call ale#Set('php_langserver_executable', 'php-language-server.php')
 call ale#Set('php_langserver_use_global', get(g:, 'ale_use_global_executables', 0))
 
 function! ale_linters#php#langserver#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') : ''