Add "paste" how-to guide (#2221)

## 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

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+# How-to guides
+
+This section contains some how-to guides for common tasks.
+
+## How do I paste to a target?
+
+`"paste to air"`
+
+To replace a target with the contents of the clipboard, say `"paste to <target>"`.
+
+:::info
+
+`"to <target>"` is an example of a Destination. See [Destinations](reference/destinations.md) for more information.
+
+:::

docs/user/reference/destinations.md

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+# Destinations
+
+Some actions expect a destination, rather than a target. Destinations combine a preposition and a target, to define a place and behavior for a Cursorless action.
+
+## `"to <target>"`
+
+Replaces the target.
+
+For example, `"paste to air"` replaces the token with a hat over the `a` with the contents of the clipboard.
+
+## `"after <target>"`
+
+Inserts after the target, adding delimiters as appropriate.
+
+For example, `"paste after air"` inserts a space after the token with a hat over the `a`, followed by the contents of the clipboard.
+
+## `"before <target>"`
+
+Inserts before the target, adding delimiters as appropriate.
+
+For example, `"paste before air"` inserts a space before the token with a hat over the `a`, then places the contents of the clipboard before the space.