Add CSS text-underline-position: auto and other values' specs (#26786)

* Add auto value to text-underline-position CSS property; add specs

* Apply suggestions from code review

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

---------

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

Author: Elchi3

css/properties/text-underline-position.json

@@ -46,8 +46,46 @@
             "deprecated": false
           }
         },
+        "auto": {
+          "__compat": {
+            "spec_url": "https://drafts.csswg.org/css-text-decor/#underline-auto",
+            "tags": [
+              "web-features:text-underline-position"
+            ],
+            "support": {
+              "chrome": {
+                "version_added": "33"
+              },
+              "chrome_android": "mirror",
+              "edge": "mirror",
+              "firefox": {
+                "version_added": "74"
+              },
+              "firefox_android": "mirror",
+              "ie": {
+                "version_added": "6"
+              },
+              "oculus": "mirror",
+              "opera": "mirror",
+              "opera_android": "mirror",
+              "safari": {
+                "version_added": "12.1"
+              },
+              "safari_ios": "mirror",
+              "samsunginternet_android": "mirror",
+              "webview_android": "mirror",
+              "webview_ios": "mirror"
+            },
+            "status": {
+              "experimental": false,
+              "standard_track": true,
+              "deprecated": false
+            }
+          }
+        },
         "from-font": {
           "__compat": {
+            "spec_url": "https://drafts.csswg.org/css-text-decor-4/#valdef-text-underline-position-from-font",
             "tags": [
               "web-features:text-underline-position"
             ],
@@ -84,6 +122,7 @@
         },
         "left": {
           "__compat": {
+            "spec_url": "https://drafts.csswg.org/css-text-decor/#underline-left",
             "tags": [
               "web-features:text-underline-position"
             ],
@@ -120,6 +159,7 @@
         },
         "right": {
           "__compat": {
+            "spec_url": "https://drafts.csswg.org/css-text-decor/#underline-left",
             "tags": [
               "web-features:text-underline-position"
             ],
@@ -156,6 +196,7 @@
         },
         "under": {
           "__compat": {
+            "spec_url": "https://drafts.csswg.org/css-text-decor/#underline-under",
             "tags": [
               "web-features:text-underline-position"
             ],