Add JSON schema support

docs/configuration/schema.md

@@ -0,0 +1,47 @@
+---
+icon: material/new-box
+---
+
+!!! question "Since sing-box 1.14.0"
+
+# JSON Schema
+
+sing-box provides a JSON Schema Draft 2020-12 for configuration files.
+Compatible editors can use it for completion and validation.
+
+### Structure
+
+```json
+{
+  "$schema": "https://sing-box.sagernet.org/schema.json"
+}
+```
+
+### Fields
+
+#### $schema
+
+The schema URI used by compatible editors.
+This field does not affect sing-box runtime behavior.
+
+The schema published with this documentation is available at
+[sing-box.sagernet.org/schema.json](https://sing-box.sagernet.org/schema.json).
+
+### Generate
+
+Use the following command to generate a schema matching the installed binary:
+
+```bash
+sing-box schema -o schema.json
+```
+
+Without `--output`, the schema is written to standard output.
+The generated schema reflects the features included in the current build.
+
+You can then reference the local schema from a configuration file:
+
+```json
+{
+  "$schema": "./schema.json"
+}
+```