Draft page about including devices in plans

docs/how-to/include-devices-in-plans.md

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+# Include Devices in Plans
+
+There are three main ways to include dodal devices in plans
+
+## 1. Pass as Argument
+
+```python
+import bluesky.plans as bp
+
+from bluesky.protocols import Readable
+from bluesky.utils import MsgGenerator
+from dodal.beamlines import i22
+
+def my_plan(detector: Readable) -> MsgGenerator:
+    yield from bp.count([detector])
+
+RE(my_plan(i22.saxs()))
+```
+
+This is useful for generic plans that can run on a variety of devices and are not designed with any specific device in mind.
+
+## 2. Pass as Default Argument
+
+```python
+import bluesky.plans as bp
+
+from bluesky.protocols import Readable
+from bluesky.utils import MsgGenerator
+from dodal.beamlines import i22
+
+def my_plan(detector: Readable = i22.saxs(connect_immediately=False)) -> MsgGenerator:
+    yield from bp.count([detector])
+
+RE(my_plan()))
+```
+
+This is useful for plans that will usually, but not exclusively, use the same device.
+
+## 3. Instantiate Within the Plan
+
+```python
+import bluesky.plans as bp
+import ophyd_async.plan_stubs as ops
+
+from bluesky.protocols import Readable
+from bluesky.utils import MsgGenerator
+from dodal.beamlines import i22
+
+def my_plan() -> MsgGenerator:
+    detector = i22.saxs(connect_immediately=False)
+    # We need to connect via the stub instead of directly 
+    # so that the RunEngine performs the connection in the
+    # correct event loop
+    yield from ops.ensure_connected(detector)
+    yield from bp.count([detector])
+
+RE(my_plan()))
+```
+
+This is useful for plans that are designed to only ever work with a specific device.