add `--no-daemon` and `--spin-time` explanation in readme.

[fujitatomoya]

address part of https://github.com/ros2/sros2/issues/306

[fujitatomoya]

i think we want to backport this to jazzy at least.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 77.35%. Comparing base (07608ab) to head (333f630).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## rolling #307 +/- ## ======================================== Coverage 77.35% 77.35% ======================================== Files 25 25 Lines 627 627 Branches 66 66 ======================================== Hits 485 485 Misses 121 121 Partials 21 21 ``` | [Flag](https://app.codecov.io/gh/ros2/sros2/pull/307/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ros2) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/ros2/sros2/pull/307/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ros2) | `77.35% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ros2#carryforward-flags-in-the-pull-request-comment) to find out more.

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[mikaelarguedas]

@Mergifyio backport jazzy

[mergify[bot]]

backport jazzy

✅ Backports have been created

* [#308 add `--no-daemon` and `--spin-time` explanation in readme. (backport #307)](https://github.com/ros2/sros2/pull/308) has been created for branch `jazzy`