Merge pull request #5674 from churchtools/default-username

Add url param `defaultUsername` to prefill the login username field

src/components/structures/MatrixChat.tsx

@@ -2091,6 +2091,7 @@ export default class MatrixChat extends React.PureComponent<IProps, IState> {
                     onForgotPasswordClick={showPasswordReset ? this.onForgotPasswordClick : undefined}
                     onServerConfigChange={this.onServerConfigChange}
                     fragmentAfterLogin={fragmentAfterLogin}
+                    defaultUsername={this.props.startingFragmentQueryParams.defaultUsername}
                     {...this.getServerProperties()}
                 />
             );