[FEATURE] Pass directly a JSON Manifest Object instead of Filepath on webInstallButton

[rainerfritz]

Hi!

In my application, I am getting the manifest as JSON object from my nodejs server. Currently I am using the esp-web-install-button, which is really awesome, thanks! Currently I could only find the possibility to pass the pathname of the manifest file. Is there a possibility to pass the object, avoiding a physical for every version and board we are supporting.

THX
Rainer