doc: fix the few non-unique id attributes on headings in the docs

Since we're now providing visible anchor links, it's important that
ID attributes on headings are genuinely unique.

Author: johnbartholomew

doc/_stdlib_gen/stdlib.jsonnet

@@ -43,7 +43,7 @@ local fieldDescription(f) =
 
 local fieldDoc(f, prefix) =
   [
-    in_panel(html.h4({ id: f.name }, prefix + '.' + f.name + fieldParams(f))),
+    in_panel(html.h4({ id: 'std-' + f.name }, prefix + '.' + f.name + fieldParams(f))),
     in_panel([
       if std.objectHas(f, 'availableSince') then (
         html.p(

doc/learning/getting_started.html

@@ -106,7 +106,7 @@ <h3 id="example">Example</h3>
 <div class="hgroup">
   <div class="hgroup-inline">
     <div class="panel">
-      <h3 id="text_output">Generating non-JSON output</h3>
+      <h3 id="text-output">Generating non-JSON output</h3>
     </div>
     <div style="clear: both"></div>
   </div>

doc/learning/tools.html

@@ -169,7 +169,7 @@ <h2 id="formatter">Formatter Demo</h2>
 <div class="hgroup">
   <div class="hgroup-inline">
     <div class="panel">
-      <h2 id="formatter">Linter</h2>
+      <h2 id="formatter-linter">Linter</h2>
     </div>
     <div style="clear: both"></div>
   </div>
@@ -194,7 +194,7 @@ <h2 id="formatter">Linter</h2>
 <div class="hgroup">
   <div class="hgroup-inline">
     <div class="panel">
-      <h2 id="formatter">Bazel Jsonnet Rules</h2>
+      <h2 id="formatter-bazel">Bazel Jsonnet Rules</h2>
     </div>
     <div style="clear: both"></div>
   </div>

doc/learning/tutorial.html

@@ -551,7 +551,7 @@ <h2 id="parameterize-entire-config">Parameterize Entire Config</h2>
 <div class="hgroup">
   <div class="hgroup-inline">
     <div class="panel">
-      <h3 id="parameterize-entire-config">External variables</h3>
+      <h3 id="external-variables">External variables</h3>
     </div>
     <div style="clear: both"></div>
   </div>
@@ -631,7 +631,7 @@ <h3 id="parameterize-entire-config">External variables</h3>
 <div class="hgroup">
   <div class="hgroup-inline">
     <div class="panel">
-      <h3 id="parameterize-entire-config">Top-level arguments</h3>
+      <h3 id="top-level-arguments">Top-level arguments</h3>
     </div>
     <div style="clear: both"></div>
   </div>
@@ -714,7 +714,7 @@ <h3 id="parameterize-entire-config">Top-level arguments</h3>
 <div class="hgroup">
   <div class="hgroup-inline">
     <div class="panel">
-      <h2 id="oo">Object-Orientation</h2>
+      <h2 id="object-orientation">Object-Orientation</h2>
     </div>
     <div style="clear: both"></div>
   </div>