docs: Update README.md

Author: l4rm4nd

README.md

@@ -13,12 +13,15 @@ docker run -it -rm -p 5000:5000 ghcr.io/l4rm4nd/cvss-api:latest
 Afterwards, you can utilize the API server:
 
 ````
+# query CVSS 2.0 vector
 curl "http://127.0.0.1:5000/cvss?vector=CVSS:2.0/AV:N/AC:L/Au:N/C:C/I:C/A:C"
+# query CVSS 3.1 vector
 curl "http://127.0.0.1:5000/cvss?vector=CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
+# query CVSS 4.0 vector
 curl "http://127.0.0.1:5000/cvss?vector=CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
 ````
 
-The API will respond with the following JSON:
+The API will respond with the following example JSON:
 
 ````
 {
@@ -29,3 +32,8 @@ The API will respond with the following JSON:
 ````
 
 Combine with an TLS reverse proxy. CORS is already allowed on the Flask application.
+
+> [!TIP]
+> For CVSS 4.0, the API server defines `Subsequent System Impact Metrics` as optional.
+> 
+> Therefore, you can neglect `SC`, `SI` and `SA` from your provided vector string. The backend will automatically set those to `N` (None).