feat(readme): mention the most common schema version

lib/readmeBuilder.js

@@ -10,15 +10,32 @@
  * governing permissions and limitations under the License.
  */
 const {
-  map, pipe, filter, list: flist, mapSort,
+  map, pipe, filter, list: flist, mapSort, uniq,
 } = require('ferrum');
 const {
   root, paragraph, text, heading, list, listItem, link, inlineCode,
 } = require('mdast-builder');
+const i18n = require('es2015-i18n-tag').default;
 const s = require('./symbols');
 const { gentitle, gendescription } = require('./formattingTools');
 const { keyword } = require('./keywords');
 
+function makeversionnote(schemas) {
+  const versions = flist(uniq(schemas
+    .map(schema => schema[keyword`$schema`])
+    .filter(e => !!e)));
+
+  if (versions.length === 1) {
+    return [
+      heading(2, text(i18n`Version Note`)),
+      paragraph([
+        text('The schemas linked above follow the JSON Schema Spec version: '),
+        inlineCode(versions[0]),
+      ]),
+    ];
+  }
+  return [];
+}
 
 /**
  * Generate the README.md
@@ -64,6 +81,8 @@ function build({ readme = true }) {
 
         heading(3, text('Arrays')),
         list('unordered', bytype('array')),
+
+        ...makeversionnote(schemas),
       ]);
 
       // console.log(inspect(readmenode));

schemasupport.md

@@ -1,10 +1,10 @@
 # JSON Schema Spec Coverage Report
 
-This report lists the keywords of the JSON Schema spec that are covered in the tests. The overall coverage is 82%
+This report lists the keywords of the JSON Schema spec that are covered in the tests. The overall coverage is 84%
 
 ## The JSON Schema Core Vocabulary
 
-Coverage for [The JSON Schema Core Vocabulary](https://json-schema.org/draft/2019-09/json-schema-core.html#rfc.section.8.1) is 44%.
+Coverage for [The JSON Schema Core Vocabulary](https://json-schema.org/draft/2019-09/json-schema-core.html#rfc.section.8.1) is 55%.
 
 | Keyword            | Supported |
 | :----------------- | --------- |
@@ -15,7 +15,7 @@ Coverage for [The JSON Schema Core Vocabulary](https://json-schema.org/draft/201
 | `$recursiveAnchor` | No        |
 | `$recursiveRef`    | No        |
 | `$ref`             | Yes       |
-| `$schema`          | No        |
+| `$schema`          | Yes       |
 | `$vocabulary`      | No        |
 
 ## A Vocabulary for Applying Subschemas

test/readmeBuilder.test.js

@@ -35,6 +35,7 @@ describe('Testing Readme Builder', () => {
 
     assertMarkdown(result)
       .contains('# README')
+      .contains('The schemas linked above')
       .fuzzy`
 ## Top-level Schemas