add stub completion provider from example

.vscode/launch.json

@@ -1,16 +1,18 @@
-// A launch configuration that launches the extension inside a new window
+// A launch configuration that compiles the extension and then opens it inside a new window
 // Use IntelliSense to learn about possible attributes.
 // Hover to view descriptions of existing attributes.
 // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
 {
   "version": "0.2.0",
   "configurations": [
     {
-      "name": "Extension",
+      "name": "Run Extension",
       "type": "extensionHost",
       "request": "launch",
       "runtimeExecutable": "${execPath}",
-      "args": ["--extensionDevelopmentPath=${workspaceFolder}", "${workspaceFolder}/test/test.md"]
+      "args": ["--extensionDevelopmentPath=${workspaceFolder}", "${workspaceFolder}/test/"],
+      "outFiles": ["${workspaceFolder}/out/**/*.js"],
+      "preLaunchTask": "npm: watch"
     }
   ]
 }

.vscode/tasks.json

@@ -0,0 +1,20 @@
+// See https://go.microsoft.com/fwlink/?LinkId=733558
+// for the documentation about the tasks.json format
+{
+	"version": "2.0.0",
+	"tasks": [
+		{
+			"type": "npm",
+			"script": "watch",
+			"problemMatcher": "$tsc-watch",
+			"isBackground": true,
+			"presentation": {
+				"reveal": "never"
+			},
+			"group": {
+				"kind": "build",
+				"isDefault": true
+			}
+		}
+	]
+}

README.md

@@ -1,5 +1,10 @@
 # VS Code Markdown Notes
 
+### dev
+
+Run `npm install` first.
+
 ### Helpful Links
 
-- https://flight-manual.atom.io/hacking-atom/sections/creating-a-legacy-textmate-grammar/
+- completion: https://github.com/microsoft/vscode-extension-samples/blob/master/completions-sample/src/extension.ts
+- syntax: https://flight-manual.atom.io/hacking-atom/sections/creating-a-legacy-textmate-grammar/