Add & fix props types. React ^v18 peer support

• Allow ^v18 of react and react-dom as peer dependencies
• Add children props types for React v18
• Fix threshold prop type
• Upgrade dev and peer dependencies to the latest versions
• Fix demo and test img src, fix few old test cases
• Add React v17 - enzyme dependency for testing

Note: In case this version throws toString is not defined error on codesandbox, try using 0.6.11 or this version on stackblitz.
According to codesandbox, something seems broken on the IntersectionObserver dev dependency utils, toString after v0.6.11.
For eg: stackblitz example for v0.7.0