plugins: fix core peer-dep version

packages/cli/templates/default-plugin/package.json.hbs

@@ -22,7 +22,7 @@
     "jest-fetch-mock": "^3.0.3"
   },
   "peerDependencies": {
-    "@backstage/core": "^0.1.0",
+    "@backstage/core": "^{{version}}",
     "@material-ui/core": "^4.9.1",
     "@material-ui/icons": "^4.9.1",
     "@material-ui/lab": "4.0.0-alpha.45",

plugins/home-page/package.json

@@ -26,7 +26,7 @@
     "react-dom": "^16.12.0"
   },
   "peerDependencies": {
-    "@backstage/core": "^0.1.0",
+    "@backstage/core": "^0.1.1-alpha.1",
     "@material-ui/core": "^4.9.1",
     "@material-ui/icons": "^4.9.1",
     "@material-ui/lab": "4.0.0-alpha.45",

plugins/welcome/package.json

@@ -22,7 +22,7 @@
     "@types/testing-library__jest-dom": "5.0.2"
   },
   "peerDependencies": {
-    "@backstage/core": "^0.1.0",
+    "@backstage/core": "^0.1.1-alpha.1",
     "@material-ui/core": "^4.9.1",
     "@material-ui/icons": "^4.9.1",
     "@material-ui/lab": "4.0.0-alpha.45",