build: upgrade to lerna v6 (#1011)

Fixes #864

Author: mattrunyon

lerna.json

@@ -1,7 +1,6 @@
 {
-  "packages": [
-    "packages/*"
-  ],
+  "packages": ["packages/*"],
   "useWorkspaces": true,
+  "useNx": false,
   "version": "0.28.0"
 }

nx.json

@@ -0,0 +1,71 @@
+{
+  "tasksRunnerOptions": {
+    "default": {
+      "runner": "nx/tasks-runners/default",
+      "options": {
+        "cacheableOperations": [
+          "build",
+          "build:babel",
+          "build:sass",
+          "svgo-dh",
+          "svgo-vs",
+          "build:icons",
+          "build:js"
+        ]
+      }
+    }
+  },
+  "namedInputs": {
+    "default": [
+      "{projectRoot}/**/*",
+      "!{projectRoot}/dist/**/*",
+      "!{projectRoot}/build/**/*",
+      "!{projectRoot}/css/**/*",
+      "!{projectRoot}/tsconfig.tsbuildinfo"
+    ],
+    "build": [
+      "default",
+      "!{projectRoot}/**/*.test.*",
+      "!{projectRoot}/test/**/*",
+      "!{projectRoot}/**/__mocks__/**/*"
+    ]
+  },
+  "targetDefaults": {
+    "build": {
+      "inputs": ["build", "^build", "{workspaceRoot}/babel.config.js"],
+      "dependsOn": ["^build"],
+      "outputs": ["{projectRoot}/build", "{projectRoot}/dist"]
+    },
+    "build:babel": {
+      "inputs": [
+        "build",
+        "!{projectRoot}/**/*.scss",
+        "{workspaceRoot}/babel.config.js"
+      ],
+      "outputs": [
+        "{projectRoot}/dist/**/*.js",
+        "{projectRoot}/dist/**/*.js.map"
+      ]
+    },
+    "build:sass": {
+      "inputs": ["{projectRoot}/**/*.scss"],
+      "outputs": [
+        "{projectRoot}/css",
+        "{projectRoot}/dist/**/*.css",
+        "{projectRoot}/dist/**/*.css.map"
+      ]
+    },
+    "svgo-dh": {
+      "outputs": ["{projectRoot}/dist/svg/dh"]
+    },
+    "svgo-vs": {
+      "outputs": ["{projectRoot}/dist/svg/vs"]
+    },
+    "build:icons": {
+      "outputs": ["{projectRoot}/dist/svg"]
+    },
+    "build:js": {
+      "outputs": ["{projectRoot}/dist", "!{projectRoot}/dist/svg"]
+    }
+  }
+}