chore: Indent JSON files with 4 spaces

[szepeviktor]

As all JSON files are currently indented with 4 spaces.

From #7478 (comment)

[coveralls]

coverage: 94.922%. remained the same
when pulling c417955 on szepeviktor:json4
into e1672a4 on PHP-CS-Fixer:master.

[szepeviktor]

double indent detector for any file

<?php

const INDENT_CHAR = ' ';
const INDENT_SIZE = 4;
const END_OF_LINE = "\n";

$filePath = $argv[1];
$contents = file_get_contents($filePath);
if ($contents === false) {
    exit(11);
}

$currentIndent = 0;
foreach (explode(END_OF_LINE, $contents) as $lineNumber => $line) {
    $indent = strspn($line, INDENT_CHAR);
    if ($indent > $currentIndent + INDENT_SIZE) {
        error_log(sprintf("Indentation size doesn't match in %s:%d", $filePath, $lineNumber + 1));
        exit(10);
    }

    $currentIndent = $indent;
}