Add strict types declaration (#7534)

Deploy script won't allow themes to be commited without this
declaration.
Recent previous case: https://github.com/Automattic/themes/pull/7529

beep/functions.php

@@ -7,7 +7,7 @@
  * @package Beep
  * @since Beep 1.0
  */
-
+declare( strict_types = 1 );
 
 if ( ! function_exists( 'beep_support' ) ) :
 

ici/functions.php

@@ -7,7 +7,7 @@
  * @package Ici
  * @since Ici 1.0
  */
-
+declare( strict_types = 1 );
 
 if ( ! function_exists( 'ici_support' ) ) :
 

indice/functions.php

@@ -8,6 +8,8 @@
  * @since indice 1.0
  */
 
+declare( strict_types = 1 );
+
 if ( ! function_exists( 'indice_support' ) ) :
 
 	/**

spiel/functions.php

@@ -7,7 +7,7 @@
  * @package Spiel
  * @since Spiel 1.0
  */
-
+declare( strict_types = 1 );
 
 if ( ! function_exists( 'spiel_support' ) ) :
 

xanadu/functions.php

@@ -7,7 +7,7 @@
  * @package Xanadu
  * @since Xanadu 1.0
  */
-
+declare( strict_types = 1 );
 
 if ( ! function_exists( 'xanadu_support' ) ) :