vscode: update editor settings and commit constraints

Enable trailing whitespace trimming, insert final newline, and force LF.
Configure git input validation to warn if subject exceeds 60 characters
or if body lines exceed 75 characters.

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>

.vscode/settings.json

@@ -1,3 +1,10 @@
 {
-    "git.alwaysSignOff": true
-}
+    "git.alwaysSignOff": true,
+    "files.trimTrailingWhitespace": true,
+    "files.insertFinalNewline": true,
+    "files.trimFinalNewlines": true,
+    "files.eol": "\n",
+    "git.inputValidation": true,
+    "git.inputValidationSubjectLength": 60,
+    "git.inputValidationLineLength": 75
+}