Add Missing Localizable Strings

[mplusb]

Is your feature request related to a problem? Please describe.

There are some strings can be localized, listed as the following.
\include\Core\UI\Page\Check_Email_Settings_Page.php

Line 157
<button id="install_wp_smtp" class="button" data-slug="wp-smtp" data-action="<?php echo ( 'install' == $smtp_status ? 'install' : 'activate' ); ?>" data-activation_url="<?php echo $activate_url; ?>"><?php echo sprintf( esc_html__( '%s SMTP', 'check-email' ), ( 'install' == $smtp_status ? esc_html__( 'Install', 'check-email' ) : esc_html__( 'Activate', 'check-email' ) ) ); ?></button>

Line 158
<div id="install_wp_smtp_info"> <p><?php echo sprintf( esc_html__( 'Click to %s WP SMTP', 'check-email' ), ( 'install' == $smtp_status ? esc_html__( 'install', 'check-email' ) : esc_html__( 'activate', 'check-email' ) ) ) ; ?> </p></div>

assets\js\admin\checkemail.js
Line 85
Activating plugin

Additional context
https://wordpress.org/support/topic/add-missing-localizable-strings/