Apply suggestions from code review

Co-authored-by: Wilco Fiers <[email protected]>

act-rules-format/act-rules-format.bs

@@ -102,6 +102,8 @@ An ACT Rule <em class="rfc2119">must</em> consist of at least the following item
 * [Background] (#background)
     * [Assumptions](#assumptions)
     * [Accessibility Support](#accessibility-support)
+    * [Related Rules (optional)](#related-rules)
+    * [Other Resources (optional)](#other-resources)
 * [Test Cases](#test-cases)
 * [Rule Versions](#rule-versions)
 * [Glossary](#glossary)
@@ -509,7 +511,7 @@ All expectations of a [=composite rule=] <em class="rfc2119">must</em> describe
 Background {#background}
 -----------------------------------
 
-An ACT Rule's Background <em class="rfc2119">must</em> contain the Assumptions and Accessibility Support sections. Additional information <em class="rfc2119">may</em> be included about the development of the rule, or references to relevant reading in Other Resources, or Related Rules. Whenever a  is included in the rule, the relationship to the relevant reading can be specified. Examples of relevant background references for a rule for a [Web Content Accessibility Guidelines](https://www.w3.org/WAI/standards-guidelines/wcag/) [[WCAG]] success criterion could be [WCAG 2.1 Understanding documents](https://www.w3.org/WAI/WCAG21/Understanding/), [WCAG 2.1 Techniques](https://www.w3.org/WAI/WCAG21/Techniques/), or [WAI-ARIA 1.1](https://www.w3.org/TR/wai-aria/), CSS [[css-2018]], or HTML [[HTML]] specifications.
+An ACT Rule's Background <em class="rfc2119">must</em> contain the Assumptions and Accessibility Support sections. Additional information <em class="rfc2119">may</em> be included about the development of the rule, or references to relevant reading in Other Resources, or Related Rules. Whenever a reference is included in the rule, the relationship to the relevant reading can be specified. Examples of relevant background references for a rule for a [Web Content Accessibility Guidelines](https://www.w3.org/WAI/standards-guidelines/wcag/) [[WCAG]] success criterion could be [WCAG 2.1 Understanding documents](https://www.w3.org/WAI/WCAG21/Understanding/), [WCAG 2.1 Techniques](https://www.w3.org/WAI/WCAG21/Techniques/), or [WAI-ARIA 1.1](https://www.w3.org/TR/wai-aria/), CSS [[css-2018]], or HTML [[HTML]] specifications.
 
 
 ### Assumptions ### {#assumptions}