feat: 3507 - added mandatory icons and optional hints to packagings (#…

…3514)

New files:
* `counter-dark.svg`
* `counter-light.svg`
* `material.svg`
* `quantity.svg`
* `recycling.svg`
* `shape.svg`
* `weight.svg`

Impacted files:
* `app_en.arb`: added hint labels for material and weight
* `edit_new_packagings.dart`: added mandatory icons and optional hints
* `explanation_widget.dart`: unrelated refactoring
* `pubspec.yaml`: added a dedicated asset folder for packagings
* `simple_input_widget.dart`: unrelated refactoring

packages/smooth_app/lib/l10n/app_en.arb

@@ -1803,6 +1803,10 @@
     "@edit_packagings_element_field_material": {
         "description": "Field label"
     },
+    "edit_packagings_element_hint_material": "Sometimes, the materials like ♵ are hidden below the pack, in 3D, on the plastic.",
+    "@edit_packagings_element_hint_material": {
+        "description": "Field verbose hint, more like an info than a text field hint"
+    },
     "edit_packagings_element_field_recycling": "Recycling instruction",
     "@edit_packagings_element_field_recycling": {
         "description": "Field label"
@@ -1815,5 +1819,9 @@
     "@edit_packagings_element_field_weight": {
         "description": "Field label"
     },
+    "edit_packagings_element_hint_weight": "For accurate packaging weight measurements, please clean any food residue and then dry any water.",
+    "@edit_packagings_element_hint_weight": {
+        "description": "Field verbose hint, more like an info than a text field hint"
+    },
     "feed_back": "Feedback"
 }