feat: add config file with envalid validation

Signed-off-by: Mike Murray <hellomikemurray@gmail.com>

src/config.js

@@ -0,0 +1,28 @@
+import envalid from "envalid";
+
+const config = {
+  PUBLIC_GRAPHQL_API_URL: process.env.PUBLIC_GRAPHQL_API_URL,
+  PUBLIC_OIDC_CLIENT_ID: process.env.PUBLIC_OIDC_CLIENT_ID,
+  PUBLIC_OIDC_URL: process.env.PUBLIC_OIDC_URL,
+  PUBLIC_ROOT_URL: process.env.PUBLIC_ROOT_URL
+};
+
+export default envalid.cleanEnv(config, {
+  PUBLIC_GRAPHQL_API_URL: envalid.str({
+    desc: "A URL that is accessible from browsers and accepts GraphQL POST requests over HTTP",
+    example: "http://localhost:3000/graphql"
+  }),
+  PUBLIC_OIDC_CLIENT_ID: envalid.str({
+    default: "reaction-admin-core",
+    desc: "The OAuth2 client ID to use for authentication flows from the browser",
+    example: "reaction-admin-core"
+  }),
+  PUBLIC_OIDC_URL: envalid.url({
+    desc: "An OAuth2 OpenID Connect compliant URL",
+    example: "http://localhost:4444"
+  }),
+  PUBLIC_ROOT_URL: envalid.url({
+    desc: "The canonical root URL for the Reaction Admin Core site",
+    example: "http://localhost:8081"
+  })
+});