Update doc about webhooks based on the latest changes.

• Fix the doc about original settings
• Add new config options which works as current doc describes

What needs to be updated:

• Chapter 6: Use upstream example or create a link to upstream example [1]?
• Chapter 7: Table, Depricate parameter and update parameter description (upstream description [2]): webImageStream.webSources.webSourcesParams.genericWebHookSecret and githubWebHookSecret
• Chapter 7: Table, Add following parameters (upstream description [1]): webhookSecrets.generic, webhookSecrets.github, webhookSecrets.gitlab

[1] https://github.com/web-servers/jws-operator/blob/main/Parameters.md#webhooksecrets
[2] https://github.com/web-servers/jws-operator/blob/main/Parameters.md#deprecated---use-webhooksecrets-instead-genericwebhooksecret-websourcesparams