feat: Allow extension capability keys to contain dot characters

src/main/java/io/appium/java_client/remote/options/W3CCapabilityKeys.java

@@ -23,7 +23,7 @@
 public class W3CCapabilityKeys implements Predicate<String> {
     public static final W3CCapabilityKeys INSTANCE = new W3CCapabilityKeys();
     private static final Predicate<String> ACCEPTED_W3C_PATTERNS = Stream.of(
-                    "^[\\w-]+:.*$",
+                    "^[\\w-\\.]+:.*$",
                     "^acceptInsecureCerts$",
                     "^browserName$",
                     "^browserVersion$",

src/test/java/io/appium/java_client/remote/options/BaseOptionsTest.java

@@ -0,0 +1,24 @@
+package io.appium.java_client.remote.options;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class BaseOptionsTest {
+
+    @ParameterizedTest
+    @CsvSource({
+        "test, appium:test",
+        "appium:test, appium:test",
+        "browserName, browserName",
+        "digital.ai:accessKey, digital.ai:accessKey",
+        "digital-ai:accessKey, digital-ai:accessKey",
+        "digital-ai:my_custom-cap:xyz, digital-ai:my_custom-cap:xyz",
+        "digital-ai:my_custom-cap?xyz, digital-ai:my_custom-cap?xyz",
+    })
+    void verifyW3CMapping(String capName, String expected) {
+        var w3cName = BaseOptions.toW3cName(capName);
+        assertEquals(expected, w3cName);
+    }
+}