docs: update readme

Author: asadali145

README.rst

@@ -51,7 +51,13 @@ Environment Variables
 * ``AUTHN_MINIMAL_HEADER`` - A boolean flag which hides the main menu, user menu, and logged-out
   menu items when truthy.  This is intended to be used in micro-frontends like
   frontend-app-authentication in which these menus are considered distractions from the user's task.
-
+* ``DASHBOARD_URL`` - The URL of the dashboard page. If not set the default ``<LMS_BASE_URL>/dashboard`` is used.
+* ``EXTERNAL_ACCOUNT_PROFILE_URL`` - An optional URL to the external profile page. If not set then default
+  internal profile page ``<ACCOUNT_PROFILE_URL>/u/<username>`` is used.
+* ``SHOW_FULLNAME`` - A boolean flag to display ``full name`` of the user in the header.
+  Defaults to ``false`` and ``username`` is displayed.
+* ``SHOW_SETTINGS_LABEL`` - A boolean flag to use `Settings` label instead of `Account` for the Account Settings page.
+  Defaults to ``false`` and uses the ``Account`` label.
 Installation
 ============
 
@@ -184,4 +190,4 @@ Please do not report security issues in public. Please email [email protected]
 .. |license| image:: https://img.shields.io/npm/l/@edx/frontend-component-header.svg
    :target: @edx/frontend-component-header
 .. |semantic-release| image:: https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg
-   :target: https://github.com/semantic-release/semantic-release
+   :target: https://github.com/semantic-release/semantic-release