Add prettier to php formatters (#394)

I added prettier to the PHP formatters as prettier also works with PHP with the [php-plugin](https://github.com/prettier/plugin-php).

README.md

@@ -400,7 +400,8 @@ that caused Neoformat to be invoked.
 - PHP
   - [`php_beautifier`](http://pear.php.net/package/PHP_Beautifier),
     [`php-cs-fixer`](http://cs.sensiolabs.org/),
-    [`phpcbf`](https://github.com/squizlabs/PHP_CodeSniffer)
+    [`phpcbf`](https://github.com/squizlabs/PHP_CodeSniffer),
+    [`prettier`](https://github.com/prettier/plugin-php)
 - PowerShell
   - [`PSScriptAnalyzer`](https://github.com/PowerShell/PSScriptAnalyzer),
     [`PowerShell-Beautifier`](https://github.com/DTW-DanWard/PowerShell-Beautifier)

autoload/neoformat/formatters/php.vim

@@ -1,5 +1,5 @@
 function! neoformat#formatters#php#enabled() abort
-    return ['phpbeautifier', 'phpcsfixer', 'phpcbf']
+    return ['phpbeautifier', 'phpcsfixer', 'phpcbf', 'prettier']
 endfunction
 
 function! neoformat#formatters#php#phpbeautifier() abort
@@ -24,3 +24,12 @@ function! neoformat#formatters#php#phpcbf() abort
            \ 'valid_exit_codes': [0,1],
            \ }
 endfunction
+
+function! neoformat#formatters#php#prettier() abort
+    return {
+        \ 'exe': 'prettier',
+        \ 'args': ['--stdin-filepath', '"%:p"'],
+        \ 'stdin': 1,
+        \ 'try_node_exe': 1,
+        \ }
+endfunction

doc/neoformat.txt

@@ -382,6 +382,7 @@ SUPPORTED FILETYPES				*neoformat-supported-filetypes*
   - [`php_beautifier`](http://pear.php.net/package/PHP_Beautifier)
   - [`php-cs-fixer`](http://cs.sensiolabs.org/)
   - [`phpcbf`](https://github.com/squizlabs/PHP_CodeSniffer)
+  - [`prettier`](https://github.com/prettier/plugin-php)
 - PowerShell
   - [`PSScriptAnalyzer`](https://github.com/PowerShell/PSScriptAnalyzer),
     [`PowerShell-Beautifier`](https://github.com/DTW-DanWard/PowerShell-Beautifier)