add pps function description

[yifanff]

No description provided.

[joem-at-aceinna]

Generated an initial draft of section on the read-the-docs site that describe the synchronization process. Awaiting feedback on this topic. Once I incorporate the feedback I will close the task.

[yifanff]

customer need 1pps and 1KHz function description on both OpenIMU300 and OpenIMU330

[yifanff]

PPS application note in document should be update with the items below:

1. The PPS 1Hz signal high voltage duty cycle supported.(0.01% From 1 second interval is 100 microseconds)
2. Which kind of GNSS receiver supported.
3. How long the typical time required to finish the synchronizatron between PPS raising edge and data ready signal raising edge.
4. The stable time inteval between PPS raising edge and data ready ready signal raising edge should be clearify.
5. The PPS timestamp desription should be clearify.
   6.The different API between OpenIMU330BI and OpenIMU300ZI in open source code should be clearify.