create multi-root workspace for positron and positron-python exte…

…nsion (#6104)

Adds a multiroot workspace config file to resolve Positron Python
formatting conflicts. This will respect the different formatters from
`positron` and `positron-python` within a single workspace, so we no
longer will have to work in multiple windows!

### Release Notes

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#### New Features

- N/A

#### Bug Fixes

- Addresses #5838 by respecting formatting in both `positron` and
`positron-python` workspaces


### QA Notes

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N/A, an opt-in dev experience

positron.code-workspace

@@ -0,0 +1,10 @@
+{
+	"folders": [
+		{
+			"path": "."
+		},
+		{
+			"path": "./extensions/positron-python"
+		}
+	]
+}