Add custom errors to docs (#4480)

docs/templates/contract.hbs

@@ -57,6 +57,23 @@ import "@openzeppelin/{{__item_context.file.absolutePath}}";
 --
 {{/if}}
 
+{{#if has-errors}}
+[.contract-index]
+.Errors
+--
+{{#each inheritance}}
+{{#unless @first}}
+[.contract-subindex-inherited]
+.{{name}}
+{{/unless}}
+{{#each errors}}
+* {xref-{{anchor~}} }[`++{{name}}({{names params}})++`]
+{{/each}}
+
+{{/each}}
+--
+{{/if}}
+
 {{#each modifiers}}
 [.contract-item]
 [[{{anchor}}]]
@@ -83,3 +100,12 @@ import "@openzeppelin/{{__item_context.file.absolutePath}}";
 {{{natspec.dev}}}
 
 {{/each}}
+
+{{#each errors}}
+[.contract-item]
+[[{{anchor}}]]
+==== `[.contract-item-name]#++{{name}}++#++({{typed-params params}})++` [.item-kind]#error#
+
+{{{natspec.dev}}}
+
+{{/each}}

docs/templates/properties.js

@@ -35,6 +35,10 @@ module.exports['has-events'] = function ({ item }) {
   return item.inheritance.some(c => c.events.length > 0);
 };
 
+module.exports['has-errors'] = function ({ item }) {
+  return item.inheritance.some(c => c.errors.length > 0);
+};
+
 module.exports['inherited-functions'] = function ({ item }) {
   const { inheritance } = item;
   const baseFunctions = new Set(inheritance.flatMap(c => c.functions.flatMap(f => f.baseFunctions ?? [])));