Update README.md

Author: KyleKotowick

README.md

@@ -5,3 +5,96 @@ This module performs a deep map merge of standard Terraform maps/objects. It is
 It functions by "flattening" each input map into a map of depth 1 where each key is the full path to the value in question. It then uses the standard merge function on these flat maps, and finally it re-builds the map structure in reverse order.
 
 **Note:** Lists will be overwritten. Only maps are merged.
+
+## Usage
+```
+locals {
+  map1 = {
+    key1-1 = {
+      key1-1-1 = "value1-1-1"
+      key1-1-2 = "value1-1-2"
+      key1-1-3 = {
+        key1-1-3-1 = "value1-1-3-1"
+        key1-1-3-2 = "value1-1-3-2"
+      }
+    }
+    key1-2 = "value1-2"
+    key1-3 = {
+      key1-3-1 = "value1-3-1"
+      key1-3-2 = "value1-3-2"
+    }
+  }
+
+  map2 = {
+    key1-1 = {
+      key1-1-1 = "value1-1-1(overwrite)"
+      key1-1-3 = {
+        key1-1-3-2 = "value1-1-3-2(overwrite)"
+        key1-1-3-3 = {
+          key1-1-3-3-1 = "value1-1-3-3-1"
+        }
+      }
+      key1-1-4 = "value1-1-4"
+    }
+    key1-2 = {
+      key1-2-1 = "value1-2-1"
+      key1-2-2 = "value1-2-2"
+      key1-2-3 = {
+        key1-2-3-1 = "value1-2-3-1"
+      }
+    }
+    key1-3 = "value1-3(overwrite)"
+  }
+
+  map3 = {
+    key1-3 = "value1-3(double-overwrite)"
+    key1-2 = {
+      key1-2-3 = {
+        key1-2-3-2 = "value1-2-3-2"
+      }
+    }
+  }
+}
+
+module "deepmerge" {
+  source = "../../"
+  maps = [
+    local.map1,
+    local.map2,
+    local.map3
+  ]
+}
+
+output "merged" {
+  description = "The merged map."
+  value       = module.deepmerge.merged
+}
+
+```
+
+Output:
+```
+merged = {
+  "key1-1" = {
+    "key1-1-1" = "value1-1-1(overwrite)"
+    "key1-1-2" = "value1-1-2"
+    "key1-1-3" = {
+      "key1-1-3-1" = "value1-1-3-1"
+      "key1-1-3-2" = "value1-1-3-2(overwrite)"
+      "key1-1-3-3" = {
+        "key1-1-3-3-1" = "value1-1-3-3-1"
+      }
+    }
+    "key1-1-4" = "value1-1-4"
+  }
+  "key1-2" = {
+    "key1-2-1" = "value1-2-1"
+    "key1-2-2" = "value1-2-2"
+    "key1-2-3" = {
+      "key1-2-3-1" = "value1-2-3-1"
+      "key1-2-3-2" = "value1-2-3-2"
+    }
+  }
+  "key1-3" = "value1-3(double-overwrite)"
+}
+```