Add float support for _ping_interval

[Olegt0rr]

What do these changes do?

Add float support for _ping_interval

Are there changes in behavior for the user?

Add float support for _ping_interval

Related issue number

Closes #446

Checklist

• [x] I think the code is well written
• [x] Unit tests for the changes exist
• [x] Documentation reflects the changes

[codecov[bot]]

Codecov Report

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

Comparison is base (2be9383) 100.00% compared to head (71228ee) 100.00%. Report is 3 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #454 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 4 4 Lines 468 436 -32 Branches 51 52 +1 ========================================= - Hits 468 436 -32 ```

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