Add refreshWhenHidden and refreshWhenOffline Settings for Polling

[MattCCC]

This issue introduces two new settings for controlling the polling behavior in the fetchff plugin:

1. refreshWhenHidden: Controls whether polling continues when the window or tab is hidden (i.e., the user switches to another tab or minimizes the window).

Default: false (polling will pause when the window is hidden)
Use case: Enables the user to specify whether the polling should continue when the page is not visible. This is useful in scenarios where background data fetching is necessary.

2. refreshWhenOffline: Determines whether polling should continue when the browser detects that it's offline using navigator.onLine.

Default: false (polling will pause when the browser is offline)
Use case: Useful for cases where the user wants to control polling behavior during connectivity issues. This setting allows the user to stop or continue polling while the browser is offline.