feat: add support for baseline years (#81)

* feat: add support for baseline years

* regenerate data and address feedback

* encode/decode status and year as a string

* countably fewer

* update baseline encoding

* add test, decode in isSupported

* max year

Author: rviscomi

docs/rules/require-baseline.md

@@ -87,7 +87,9 @@ h1:has(+ h2) {
 
 This rule accepts an option object with the following properties:
 
-- `available` (default: `"widely"`) - change to `"newly"` available to allow a larger number of properties and at-rules.
+- `available` (default: `"widely"`)
+    - change to `"newly"` available to allow features that have had cross-browser support for fewer than 30 months
+    - set to a numeric baseline year, for which all features that became baseline that year or earlier should be allowed (example: `2023`)
 
 ## When Not to Use It