Add jq script for CI

scripts/shields-from-tests.jq

@@ -0,0 +1,27 @@
+{
+    # filter for "passed" and "test_count" in input objects with `"type": "suite"`
+    # and accumulate stats from all tests
+    "passed": map(select(.type == "suite" and has("passed")) | .passed) | add,
+    "total": map(select(.type == "suite" and has("test_count")) | .test_count) | add
+} | . + {
+    # calculate ratio of passed tests
+    "factor": (.passed / .total)
+} | {
+    # calculate color from test factor
+    "color": (
+        if .factor < 0.33 then
+            "red"
+        elif .factor < 0.66 then
+            "orange"
+        elif .factor < 1.0 then
+            "yellow"
+        else
+            "brightgreen"
+        end
+    ),
+    "isError": true,
+    "label": "cargo test",
+    # interpolate the shield label
+    "message": "\(.passed) / \(.total) tests",
+    "schemaVersion": 1
+}