Add VS Code settings and update Makefile (#80)

* Add VS Code settings and update Makefile

* Add settings to handout

* Update settings and Makefile

* Add vscode extensions config

---------

Co-authored-by: sgdxbc <sung@comp.nus.edu.sg>

Author: sgdxbc

handout-files/.vscode/extensions.json

@@ -0,0 +1,6 @@
+{
+    "recommendations": [
+        "josevseb.google-java-format-for-vs-code",
+        "redhat.java"
+    ]
+}

handout-files/.vscode/settings.json

@@ -0,0 +1,19 @@
+{
+    "java.project.sourcePaths": [
+        "labs/lab0-pingpong/src",
+        "labs/lab0-pingpong/tst",
+        "labs/lab1-clientserver/src",
+        "labs/lab1-clientserver/tst",
+        "labs/lab2-primarybackup/src",
+        "labs/lab2-primarybackup/tst",
+        "labs/lab3-paxos/src",
+        "labs/lab3-paxos/tst",
+        "labs/lab4-shardedstore/src",
+        "labs/lab4-shardedstore/tst",
+    ],
+    "java.project.referencedLibraries": [
+        "jars/*.jar",
+    ],
+    "java.compile.nullAnalysis.mode": "automatic",
+    "editor.defaultFormatter": "josevseb.google-java-format-for-vs-code",
+}