add boolean glossary link (#25595)

Author: estelle

files/en-us/web/html/attributes/required/index.md

@@ -7,15 +7,15 @@ browser-compat: html.elements.attributes.required
 
 {{HTMLSidebar}}
 
-The Boolean **`required`** attribute, if present, indicates that the user must specify a value for the input before the owning form can be submitted.
+The [Boolean](/en-US/docs/Glossary/Boolean/HTML) **`required`** attribute, if present, indicates that the user must specify a value for the input before the owning form can be submitted.
 
 The `required` attribute is supported by `{{HTMLElement("input/text","text")}}`, `{{HTMLElement("input/search","search")}}`, `{{HTMLElement("input/url","url")}}`, `{{HTMLElement("input/tel","tel")}}`, `{{HTMLElement("input/email","email")}}`, `{{HTMLElement("input/password","password")}}`, `{{HTMLElement("input/date","date")}}`, `{{HTMLElement("input/month","month")}}`, `{{HTMLElement("input/week","week")}}`, `{{HTMLElement("input/time","time")}}`, `{{HTMLElement("input/datetime-local","datetime-local")}}`, `{{HTMLElement("input/number","number")}}`, `{{HTMLElement("input/checkbox","checkbox")}}`, `{{HTMLElement("input/radio","radio")}}`, `{{HTMLElement("input/file","file")}}`, {{HTMLElement("input")}} types along with the {{HTMLElement("select")}} and {{HTMLElement("textarea")}} form control elements. If present on any of these input types and elements, the {{cssxref(':required')}} pseudo class will match. If the attribute is not included, the {{cssxref(':optional')}} pseudo class will match.
 
 The attribute is not supported or relevant to {{HTMLElement("input/range","range")}} and {{HTMLElement("input/color","color")}}, as both have default values. It is also not supported on {{HTMLElement("input/hidden","hidden")}} as it can not be expected that a user to fill out a form that is hidden. Nor is it supported on any of the button types, including `image`.
 
-Note `color` and `range` don't support `required`, but type `color` defaults to `#000000`, and `range` defaults to the midpoint between `min` and `max` — with `min` and `max` defaulting to 0 and 100 respectively in most browsers if not declared — so always has a value.
+Note `color` and `range` don't support `required` as both always have a value. Type `color` defaults to `#000000`. The default for `range` is the midpoint between `min` and `max` — with `min` and `max` defaulting to 0 and 100 respectively in most browsers if not declared.
 
-In the case of a same named group of {{HTMLElement("input/radio","radio")}} buttons, if a single radio button in the group has the `required` attribute, a radio button in that group must be checked, although it doesn't have to be the one on which the attribute is applied. So to improve code maintenance, it is recommended to either include the `required` attribute in every same-named radio button in the group, or else in none.
+In the case of a same named group of {{HTMLElement("input/radio","radio")}} buttons, if a single radio button in the group has the `required` attribute, a radio button in that group must be checked, although it doesn't have to be the one on which the attribute is applied. To improve code maintenance, it is recommended to either include the `required` attribute in every same-named radio button in the group, or else in none.
 
 In the case of a same named group of {{HTMLElement("input/checkbox","checkbox")}} input types, only the checkboxes with the `required` attribute are required.
 
@@ -48,7 +48,7 @@ Provide an indication to users informing them the form control is required. Ensu
     <label>Normal</label>
   </div>
   <div class="group">
-    <input type="text" required="required" />
+    <input type="text" required />
     <label>Required</label>
   </div>
   <input type="submit" />