add skipInactive option

Skip inactive time is an important and useful feature. We consider
user interaction events as active, and check next user interaction
event after apply incremental snapshot.
If next user interaction event has a time gap larger than the
threshold, we will set a dynamic speed value which will skip the
inactive time interval in about 5 seconds.

src/types.ts

@@ -95,6 +95,7 @@ export type event =
 
 export type eventWithTime = event & {
   timestamp: number;
+  delay?: number;
 };
 
 export type recordOptions = {
@@ -227,6 +228,7 @@ export type playerConfig = {
   speed: number;
   root: Element;
   loadTimeout: number;
+  skipInactive: Boolean;
 };
 
 export type playerMetaData = {