Add mountain wall recolor of asteroid rock for mappers. (#11729)

Resources/Prototypes/Entities/Structures/Walls/mountain.yml

@@ -0,0 +1,19 @@
+- type: entity
+  id: MountainRock
+  parent: AsteroidRock
+  name: mountain rock
+  description: A craggy mountain wall.
+  components:
+  - type: Sprite
+    sprite: Structures/Walls/mountain_rock.rsi
+    state: full
+
+- type: entity
+  id: MountainRockMining
+  parent: AsteroidRockMining
+  name: mountain rock
+  description: A craggy mountain wall.
+  components:
+  - type: Sprite
+    sprite: Structures/Walls/mountain_rock.rsi
+    state: full

Resources/Textures/Structures/Walls/mountain_rock.rsi/meta.json

@@ -0,0 +1,46 @@
+{
+    "version": 1,
+    "copyright": "recolor of https://github.com/discordia-space/CEV-Eris/commit/a0c067f688288aeb167157203e2170b14cfa9d7f",
+    "license": "CC-BY-SA-3.0",
+    "size": {
+        "x": 32,
+        "y": 32
+    },
+    "states": [
+        {
+            "directions": 4,
+            "name": "rock_0"
+        },
+        {
+            "directions": 4,
+            "name": "rock_1"
+        },
+        {
+            "directions": 4,
+            "name": "rock_2"
+        },
+        {
+            "directions": 4,
+            "name": "rock_3"
+        },
+        {
+            "directions": 4,
+            "name": "rock_4"
+        },
+        {
+            "directions": 4,
+            "name": "rock_5"
+        },
+        {
+            "directions": 4,
+            "name": "rock_6"
+        },
+        {
+            "directions": 4,
+            "name": "rock_7"
+        },
+        {
+            "name": "full"
+        }
+    ]
+}