Readme update

[Nirupma-Verma]

Desired Outcome

*Read.md updated for explaining the usage of provider directly from registry.terraform.io and access token authentication for example for fetching secret

Implemented Changes

Describe how the desired outcome above has been achieved with this PR. In
particular, consider:

• To support access token authentication fix is being provided in conjur-api-go (Access token change conjur-api-go#137)
• Read.md updated with example of fetching secret using registry.terraform.io and access token

Connected Issue/Story

Resolves #[https://github.com//issues/99
https://github.com//issues/69
]

CyberArk internal issue link: insert issue ID

Definition of Done

At least 1 todo must be completed in the sections below for the PR to be
merged.

Changelog

• The CHANGELOG has been updated, or
• This PR does not include user-facing changes and doesn't require a
  CHANGELOG update

Test coverage

• This PR includes new unit and integration tests to go with the code
  changes, or
• The changes in this PR do not require tests

Documentation

• Docs (e.g. READMEs) were updated in this PR
• A follow-up issue to update official docs has been filed here: insert issue ID
• This PR does not require updating any documentation

Behavior

• This PR changes product behavior and has been reviewed by a PO, or
• These changes are part of a larger initiative that will be reviewed later, or
• No behavior was changed with this PR

Security

• Security architect has reviewed the changes in this PR,
• These changes are part of a larger initiative with a separate security review, or
• There are no security aspects to these changes

[gcandiloro]

Not sure if my leaving a comment will help you add me as a reviewer, but it looks like I can leave feedback as a comment.

[gcandiloro]

A couple of minor suggestions, all else looks good.