vscode: update editor formatting and line endings settings

Enable trailing whitespace trimming, insert final newline, and force LF.

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/23750
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>

.vscode/settings.json

@@ -1,3 +1,7 @@
 {
-    "git.alwaysSignOff": true
+    "git.alwaysSignOff": true,
+    "files.trimTrailingWhitespace": true,
+    "files.insertFinalNewline": true,
+    "files.trimFinalNewlines": true,
+    "files.eol": "\n"
 }