version badge (#1000)

* version badge inspired by Plot's documentation

* badge tweaks

* more badges

---------

Co-authored-by: Mike Bostock <mbostock@gmail.com>

docs/config.md

@@ -196,7 +196,7 @@ toc: false
 
 Whether to enable [search](./search) on the project; defaults to false.
 
-## markdownIt
+## markdownIt <a href="https://github.com/observablehq/framework/releases/tag/v1.1.0" target="_blank" class="observablehq-version-badge" data-version="1.1.0" title="Added in v1.1.0"></a>
 
 A hook for registering additional [markdown-it](https://github.com/markdown-it/markdown-it) plugins. For example, to use [markdown-it-footnote](https://github.com/markdown-it/markdown-it-footnote):
 

docs/lib/echarts.md

@@ -2,7 +2,7 @@
 index: true
 ---
 
-# Apache ECharts
+# Apache ECharts <a href="https://github.com/observablehq/framework/releases/tag/v1.1.0" target="_blank" class="observablehq-version-badge" data-version="1.1.0" title="Added in v1.1.0"></a>
 
 [Apache ECharts](https://echarts.apache.org), an open-source JavaScript visualization library, is available by default as `echarts` in Markdown. You can also import it explicitly like so:
 

docs/markdown.md

@@ -18,8 +18,8 @@ The front matter supports the following options:
 - **title** — the page title; defaults to the (first) first-level heading of the page, if any
 - **toc** — if false, disables the [table of contents](./config#toc)
 - **index** — whether to index this page if [search](./search) is enabled; defaults to true for listed pages
-- **keywords** - additional words to index for [search](./search); boosted at the same weight as the title
-- **draft** — whether to skip this page during build; drafts are also not listed in the default sidebar
+- **keywords** <a href="https://github.com/observablehq/framework/releases/tag/v1.1.0" target="_blank" class="observablehq-version-badge" data-version="1.1.0" title="Added in v1.1.0"></a> - additional words to index for [search](./search); boosted at the same weight as the title
+- **draft** <a href="https://github.com/observablehq/framework/releases/tag/v1.1.0" target="_blank" class="observablehq-version-badge" data-version="1.1.0" title="Added in v1.1.0"></a> — whether to skip this page during build; drafts are also not listed in the default sidebar
 
 ## Headings
 

docs/sql.md

@@ -3,7 +3,7 @@ sql:
   gaia: ./lib/gaia-sample.parquet
 ---
 
-# SQL
+# SQL <a href="https://github.com/observablehq/framework/releases/tag/v1.2.0" target="_blank" class="observablehq-version-badge" data-version="1.2.0" title="Added in v1.2.0"></a>
 
 Observable Framework includes built-in support for client-side SQL powered by [DuckDB](./lib/duckdb). You can use SQL to query data from [CSV](./lib/csv), [TSV](./lib/csv), [JSON](./javascript/files#json), [Apache Arrow](./lib/arrow), and [Apache Parquet](./lib/arrow#apache-parquet) files, which can either be static or generated by [data loaders](./loaders).
 

docs/style.css

@@ -34,3 +34,17 @@
     display: none;
   }
 }
+
+a.observablehq-version-badge {
+  font: 500 12px var(--sans-serif);
+  display: inline-block;
+  vertical-align: top;
+  padding: 2px 8px;
+  color: var(--theme-green);
+  background: color-mix(in srgb, var(--theme-green), transparent 80%);
+  border-radius: 12px;
+}
+
+.observablehq-version-badge::before {
+  content: "^" attr(data-version);
+}