Support custom params for token request

[kaviththiranga]

Purpose

This is to support tokenBindingId for token request to be passed via sign-in method

Need to be released with
asgardeo/asgardeo-auth-js-core#256
asgardeo/asgardeo-auth-spa-sdk#174

Goals

• Address Add capability to pass custom parameters to the /oauth2/token request from the SDK level asgardeo-auth-js-core#257

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[pavinduLakshan]

Shall we link the auth-spa and js-core PRs in the PR description?