move some required dependancies to suggest

Author: Mehedi Hasan Nahid

composer.json

@@ -4,12 +4,8 @@
     "type": "php",
     "require": {
         "php": ">=5.5.9 | >=7.0",
-        "ext-curl": "*",
         "guzzlehttp/guzzle": "^6.4",
-        "ext-libxml" : "*",
-        "ext-simplexml" : "*",
         "ext-json": "*",
-        "ext-yaml": "*",
         "lib-libxml" : ">=2.6.20",
         "nahid/qarray": "^1.2",
         "guzzlehttp/psr7": "^1.6"
@@ -18,6 +14,12 @@
         "phpunit/phpunit": "^6.2",
         "symfony/var-dumper": "^3.4"
     },
+    "suggest": {
+        "ext-curl": "*",
+        "ext-libxml": "*",
+        "ext-yaml": "*",
+        "ext-simplexml" : "*"
+    },
     "license": "MIT",
     "authors": [
         {