[respeaker_ros] Add documentation for displaying Japanese /speech_to_text

[tkmtnt7000]

This PR adds documentation for getting readable Japanese voice recognition results from rostopic echo.
Users sometimes had a problem that they don't know making Japanese voice recognition results readable through rostopic echo and where the example code is.

Examples

$ rostopic echo --filter "print(m.transcript[0])" /speech_to_text
こんにちは

c.f. jsk-ros-pkg/jsk_demos#1347 (comment), jsk-ros-pkg/jsk_demos#1347 (comment)

k-okada@p51s:~$ rostopic echo /text
data: !!python/str "\u3053\u3093\u306B\u3061\u306F 1636542913.42"
---
data: !!python/str "\u3053\u3093\u306B\u3061\u306F 1636542913.52"
^Ck-okada@p51s:~$ rostopic echo /text | ascii2uni -a U -q
data: !!python/str "こんにちは 1636542916.02"

rostopic echo --filter "print('transcript: [%s]\n---'%(', '.join(map(lambda x: '\'%s\''%(x.decode('utf-8')), m.transcript))))" /speech_to_text
transcript: [' こんにちは 。', ' こんにちは あ 。', ' 今日 わ 。', ' こんにちは は 。', ' 今日 は 。']

[iory]

Does this work with python3 (noetic)?

[tkmtnt7000]

Oh, it doesn't work with python3. Thank you for letting me know.
I drop this line.

[tkmtnt7000]

I have also confirmed that the others work well with python3.

[iory]

rostopic echo --filter "print('transcript: [%s]\n---'%(', '.join(map(str, m.transcript))))" /speech_to_text is good?

[tkmtnt7000]

It's ok to use it. I'll add.