Add VSCode task how-to doc (#2239)

## Checklist

- [-] I have added
[tests](https://www.cursorless.org/docs/contributing/test-case-recorder/)
- [x] I have updated the
[docs](https://github.com/cursorless-dev/cursorless/tree/main/docs) and
[cheatsheet](https://github.com/cursorless-dev/cursorless/tree/main/cursorless-talon/src/cheatsheet)
- [-] I have not broken the cheatsheet

Author: pokey

docs/user/how-to.md

@@ -13,3 +13,36 @@ To replace a target with the contents of the clipboard, say `"paste to <target>"
 `"to <target>"` is an example of a Destination. See [Destinations](reference/destinations.md) for more information.
 
 :::
+
+## How do I run a VSCode task / bash shell command on a target?
+
+1. Add a [VSCode task](https://code.visualstudio.com/docs/editor/variables-reference) to your `tasks.json` (say `"please open tasks"`):
+
+   ```json
+   {
+     "label": "Echo",
+     "type": "shell",
+     "command": "echo",
+     "args": ["${selectedText}"]
+   }
+   ```
+
+   (replace `echo` / `Echo` with your actual command name)
+
+2. Add a spoken form to your `vscode.talon`:
+
+   ```talon
+   echo <user.cursorless_target>:
+     user.cursorless_command("setSelection", cursorless_target)
+     user.run_rpc_command("workbench.action.tasks.runTask", "Echo")
+   ```
+
+   (replace `echo` / `Echo` with your actual command name)
+
+You can now say eg `"echo air past bat"`.
+
+:::info
+
+See the [Talon-side api docs](./customization.md#cursorless-public-api) for more on creating custom Cursorless commands
+
+:::