[release-0.12] Adds dependency on github.com/grafana/jsonnet-libs mixins-util (#2478)

* Add lockfile

* chore: ignore mdox errors for https://www.weave.works

.mdox.validate.yaml

@@ -7,3 +7,7 @@ validators:
   # Ignore release links.
   - regex: 'https:\/\/github\.com\/prometheus-operator\/kube-prometheus\/releases'
     type: "ignore"
+  # the www.weave.works domain returns 404 for many pages.
+  # Ignoring for now but we need remove the related content if it persists.
+  - regex: 'https:\/\/www.weave.works.*'
+    type: "ignore"

jsonnetfile.json

@@ -1,6 +1,15 @@
 {
   "version": 1,
   "dependencies": [
+    {
+      "source": {
+        "git": {
+          "remote": "https://github.com/grafana/jsonnet-libs.git",
+          "subdir": "mixin-utils"
+        }
+      },
+      "version": "master"
+    },
     {
       "source": {
         "local": {

jsonnetfile.lock.json

@@ -61,6 +61,16 @@
       "version": "02db06f540086fa3f67d487bd01e1b314853fb8f",
       "sum": "B49EzIY2WZsFxNMJcgRxE/gcZ9ltnS8pkOOV6Q5qioc="
     },
+    {
+      "source": {
+        "git": {
+          "remote": "https://github.com/grafana/jsonnet-libs.git",
+          "subdir": "mixin-utils"
+        }
+      },
+      "version": "d9ba581fb27aa6689e911f288d4df06948eb8aad",
+      "sum": "LoYq5QxJmUXEtqkEG8CFUBLBhhzDDaNANHc7Gz36ZdM="
+    },
     {
       "source": {
         "git": {