leftcurly.md - Change string "true" to boolean true (#13)

previous code caused a warning

Author: Geokureli

haxe-checkstyle/leftcurly.md

@@ -13,7 +13,7 @@ Checks for the placement of left curly braces (`{`) for code blocks. The policy
     "props": {
         "severity": "WARNING",
         "option": "eol",
-        "ignoreEmptySingleline": "true",
+        "ignoreEmptySingleline": true,
         "tokens": [
             "CLASS_DEF",
             "ENUM_DEF",
@@ -91,4 +91,4 @@ With `ignoreEmptySingleline` set to `false`
 public function donothing() {}
 ```
 
-{{site.data.alerts.error}} Left curly should be at EOL (only linebreak or comment after curly) {{site.data.alerts.end}}
+{{site.data.alerts.error}} Left curly should be at EOL (only linebreak or comment after curly) {{site.data.alerts.end}}