add empty and in_array modifier doc

docs/designers/language-modifiers/language-modifier-empty.md

@@ -0,0 +1,10 @@
+# empty
+
+Returns true if var does not exist or has a value that is empty or equal to zero, aka falsey, see conversion to boolean. Otherwise returns false.
+
+## Basic usage
+
+```smarty
+{if $myVar|empty}it's an empty variable{/if}
+{if empty($myVar)}it's an empty variable{/if}
+```

docs/designers/language-modifiers/language-modifier-in_array.md

@@ -0,0 +1,17 @@
+# in_array
+
+test if value is contained in an array
+
+## Basic usage
+
+```smarty
+{if in_array('value2', $myarray)} value2 is in myarray{/if}
+```
+
+Can be replaced by operator *is in*
+
+```smarty
+{if 'value2' is in $myarray}value2 is in myarray{/if}
+```
+
+See Also [operators](../language-basic-syntax/language-syntax-operators.md)

mkdocs.yml

@@ -57,9 +57,11 @@ nav:
         - 'date_format': 'designers/language-modifiers/language-modifier-date-format.md'
         - 'debug_print_var': 'designers/language-modifiers/language-modifier-debug-print-var.md'
         - 'default': 'designers/language-modifiers/language-modifier-default.md'
+        - 'empty': "designers/language-modifiers/language-modifier-empty.md"
         - 'escape': 'designers/language-modifiers/language-modifier-escape.md'
         - 'from_charset': 'designers/language-modifiers/language-modifier-from-charset.md'
         - 'indent': 'designers/language-modifiers/language-modifier-indent.md'
+        - 'in_array': 'designers/language-modifiers/language-modifier-in_array.md'
         - 'is_array': 'designers/language-modifiers/language-modifier-is_array.md'
         - 'isset': 'designers/language-modifiers/language-modifier-isset.md'
         - 'join': 'designers/language-modifiers/language-modifier-join.md'