chore: move api into peer dependency (#522)

* chore: move api into peer dependency

* fix peer-api-check script

Author: Flarna

package.json

@@ -45,7 +45,11 @@
   "publishConfig": {
     "access": "public"
   },
+  "peerDependencies": {
+    "@opentelemetry/api": "^0.20.0"
+  },
   "devDependencies": {
+    "@opentelemetry/api": "0.20.0",
     "@types/mocha": "8.2.2",
     "@types/node": "14.17.2",
     "@types/webpack-env": "1.16.0",
@@ -67,7 +71,6 @@
     "webpack": "4.46.0"
   },
   "dependencies": {
-    "@opentelemetry/api": "^0.20.0",
     "@opentelemetry/core": "^0.20.0"
   }
 }