a7c15b2ac0
This PR: * Moves the dialpad and hold/transfer menu buttons into the part of the DOM that's included when a call is fullscreen'd. * Tweaks `ContextMenu` to allow menu content to be mount as a child of the current component, rather than at the root of the DOM (which was not included in the full-screen'd content). <!-- Please read https://github.com/matrix-org/matrix-js-sdk/blob/develop/CONTRIBUTING.md before submitting your pull request --> <!-- Include a Sign-Off as described in https://github.com/matrix-org/matrix-js-sdk/blob/develop/CONTRIBUTING.md#sign-off --> `Signed-off-by: Andrew Morgan <andrewm@element.io>`