Add CSS justify-items: center (#28421)

* Update justify-items.json

---------

Co-authored-by: Claas Augner <[email protected]>

Author: zhangenming

css/properties/justify-items.json

@@ -114,6 +114,39 @@
             }
           }
         },
+        "center": {
+          "__compat": {
+            "tags": [
+              "web-features:flexbox"
+            ],
+            "support": {
+              "chrome": {
+                "version_added": "52"
+              },
+              "chrome_android": "mirror",
+              "edge": "mirror",
+              "firefox": {
+                "version_added": "20"
+              },
+              "firefox_android": "mirror",
+              "oculus": "mirror",
+              "opera": "mirror",
+              "opera_android": "mirror",
+              "safari": {
+                "version_added": "9"
+              },
+              "safari_ios": "mirror",
+              "samsunginternet_android": "mirror",
+              "webview_android": "mirror",
+              "webview_ios": "mirror"
+            },
+            "status": {
+              "experimental": false,
+              "standard_track": true,
+              "deprecated": false
+            }
+          }
+        },
         "flex_context": {
           "__compat": {
             "description": "Supported in Flex Layout",