feat: implement startPosition (#3355)

* feat(android): implement startPosition

* feat(ios): implement startPosition

* feat: implement startPosition type

* docs: fix typo

* docs: update startPosition

* refactor: put startPosition inside source prop
- put startPosition inside source prop
- rename existing prop (startTime, endTime)

* docs: update startPosition property description

* fix: fix invalid assignments

* refactor: remove redundant optional chaining

* feat: allow "0" to work too

src/types/video.ts

@@ -15,8 +15,9 @@ export type ReactVideoSourceProperties = {
   mainVer?: number;
   patchVer?: number;
   headers?: Headers;
-  startTime?: number;
-  endTime?: number;
+  startPosition?: number;
+  cropStart?: number;
+  cropEnd?: number;
   title?: string;
   subtitle?: string;
   description?: string;