[silverstripe] Add method (#532)

Parse https://raw.githubusercontent.com/silverstripe/roadmap/refs/heads/main/data.json to get release information.

Relates to https://github.com/endoflife-date/endoflife.date/pull/8932.

src/silverstripe.py

@@ -0,0 +1,20 @@
+from common import dates, http
+from common.releasedata import ProductData, config_from_argv
+
+"""Fetches Silverstripe releases from https://www.silverstripe.org/software/roadmap/ JSON data."""
+
+config = config_from_argv()
+with ProductData(config.product) as product_data:
+    json = http.fetch_json(config.url)
+    for release_data in json["data"]:
+        release_name = release_data["version"]
+        release = product_data.get_release(release_name)
+
+        release_date_str = release_data.get("releaseDate")
+        release.set_release_date(dates.parse_date_or_month_year_date(release_date_str))
+
+        eoas_date_str = release_data.get("partialSupport")
+        release.set_eoas(dates.parse_date_or_month_year_date(eoas_date_str))
+
+        eol_date_str = release_data.get("supportEnds")
+        release.set_eol(dates.parse_date_or_month_year_date(eol_date_str))