add linting in vscode

.vscode/extensions.json

@@ -0,0 +1,7 @@
+{
+    "recommendations": [
+        "mshr-h.veriloghdl",
+        "zhwu95.riscv",
+        "hediet.vscode-drawio"
+    ]
+}

.vscode/settings.json

@@ -0,0 +1,8 @@
+{
+    "editor.rulers": [
+        120
+    ],
+    "editor.formatOnSave": true,
+    "verilog.linting.linter": "iverilog",
+    "verilog.linting.iverilog.arguments": "-g2012 -i -Wall",
+}