Include VSCode tasks for shared build/test behaviour

These are mostly cribbed from ziglang/vscode-zig#30, with the addition of defining zig's `main-pkg-path` to be the workspace. This permits zig files to include any file within the workspace; otherwise, `@import`s of paths outside the zig file's own directory tree will fail with a compile error.

.gitignore

@@ -1,2 +1 @@
 zig-cache/
-.vscode/

.vscode/tasks.json

@@ -0,0 +1,63 @@
+{
+  // See https://go.microsoft.com/fwlink/?LinkId=733558
+  // for the documentation about the tasks.json format
+  "version": "2.0.0",
+  "tasks": [
+    {
+        "label": "zig build-exe",
+        "type": "process",
+        "command": "zig",
+        "args": [
+            "build-exe",
+            "${file}",
+            "--main-pkg-path",
+            "${workspaceFolder}"
+        ],
+        "group": "build",
+        "presentation": {
+            "reveal": "silent",
+            "showReuseMessage": false,
+            "clear": true
+        }
+    },
+    {
+        "label": "zig run",
+        "type": "process",
+        "command": "zig",
+        "args": [
+            "run",
+            "${file}",
+            "--main-pkg-path",
+            "${workspaceFolder}"
+        ],
+        "group": {
+            "kind": "build",
+            "isDefault": true
+        },
+        "presentation": {
+            "showReuseMessage": false,
+            "clear": true
+        }
+    },
+    {
+        "label": "zig test",
+        "type": "process",
+        "command": "zig",
+        "args": [
+            "test",
+            "${file}",
+            "--main-pkg-path",
+            "${workspaceFolder}"
+        ],
+        "group": {
+            "kind": "test",
+            "isDefault": true
+        },
+        "presentation": {
+            "showReuseMessage": false,
+            "clear": true
+        },
+        "problemMatcher": []
+    }
+]
+}