Include `maskTextSelector ` in the sdk config and readme/docs & update field names

[ryan953]

Currently our documented privacy controls include (from rrweb):

• blockClass
• blockSelector
• ignoreClass
• maskAllInputs
• maskTextClass

as well as some convenience fields we've added on top.

What's missing from the docs is:

• maskTextSelector

The complete list of fields is here: https://github.com/rrweb-io/rrweb/blob/rrweb-snapshot%401.1.14/packages/rrweb/typings/types.d.ts#L135-L158

Note: reviewing the naming of these fields here

[billyvg]

@ryan953 So this intentional for maskTextSelector because we use it to mask all text nodes. We'll want to think about a way to allow exclusions for masking (and with mask all text turned on).

[billyvg]

Closing this as this is in the docs now