Fix some Bikeshed link errors and warnings (#70)

Author: CanadaHonk

index.bs

@@ -13,6 +13,7 @@ Markup Shorthands: markdown yes
 <pre class=link-defaults>
 spec:url; type:interface; text:URL
 spec:html; type:attribute; for:Window; text:navigator
+spec:fetch; type:method; text:fetch()
 </pre>
 
 Introduction {#intro}
@@ -30,7 +31,7 @@ The Web Platform is the combination of technology standards defined by organizat
 A <dfn>Web-interoperable Runtime</dfn> is any ECMAScript-based application runtime environment that implements the subset of Web Platform APIs outlined in this specification.
 While this term is intentionally broad to also encompass Web Browsers, the primary focus here is on outlining expectations for non-browser runtimes.
 
-Common API Index {#index}
+Common API Index {#api-index}
 =========================
 
 All <a>Web-interoperable Runtimes</a> conforming to this specification SHALL implement each of the following Web Platform APIs in accordance with their normative requirements except where modified here. Where any conforming runtime environment chooses (either by necessity or otherwise) to diverge from a normative requirement of the specification, clear explanations of such divergence MUST be made clearly and readily available in the documentation.
@@ -113,8 +114,8 @@ The exact type of the global scope (`globalThis`) can vary across runtimes. Most
 
 With many runtimes, adding a new global-scoped property can introduce breaking changes when the new global conflicts with existing application code. Many Web Platform APIs define global properties using the `readonly` attribute. To avoid introducing breaking changes, runtimes conforming to this specification MAY choose to ignore the `readonly` attribute for properties being added to the global scope.
 
-Requirements for navigator.userAgent
-====================================
+Requirements for navigator.userAgent {#navigator-useragent-requirements}
+========================================================================
 
 The globalThis.{{navigator}}.{{userAgent}} property is provided such that application code can reliably identify the runtime within which it is running.
 The value of the property is a string conforming to the <code class="idl"><a data-link-type="idl" href="https://datatracker.ietf.org/doc/html/rfc7231#section-5.5.3">`User-Agent`</a></code> construction in RFC 7231: