Add VS Code launch and task files

This enables building PowerShell through VS Code. The build task
launches the installed version of PowerShell and runs
`Start-PSBuild` (after importing the module).

This enables a `launch` debug task to immediately debug the `powershell`
process, without having to attach to an external process.

The defaults of `justMyCode` and `stopAtEntry` have been reversed, so
that all code is debugged, and the process is stopped at entry for
easier debugging.

Note that an interactive PowerShell process requires access to `stdin`,
which the debug console does not provide, so once it requests access,
`System.Console` will throw a (correct) exception.

.vscode/launch.json

@@ -0,0 +1,16 @@
+{
+	"version": "0.2.0",
+	"configurations": [
+		{
+			"name": "powershell",
+			"type": "coreclr",
+			"request": "launch",
+			"justMyCode": false,
+			"stopAtEntry": true,
+			"program": "${workspaceRoot}/bin/powershell",
+			"args": [ ],
+			"preLaunchTask": "build",
+			"cwd": "${workspaceRoot}"
+		}
+	]
+}

.vscode/tasks.json

@@ -0,0 +1,16 @@
+{
+	"version": "0.1.0",
+	"command": "powershell",
+	"isShellCommand": true,
+	"showOutput": "verbose",
+	"args": [ "--command" ],
+
+	"tasks": [
+		{
+			"taskName": "build",
+			"args": [ "Import-Module ${workspaceRoot}/PowerShellGitHubDev.psm1; Start-PSBuild" ],
+			"isBuildCommand": true,
+			"problemMatcher": "$msCompile"
+		}
+	]
+}