feat(gatsby-plugin-netlify): add force option to createRedirect (#8521)

Author: RobertWSaunders

Diff for: packages/gatsby-plugin-netlify/README.md

@@ -118,6 +118,8 @@ createRedirect({ fromPath: "/old-url", toPath: "/new-url", isPermanent: true })
 createRedirect({ fromPath: "/url", toPath: "/zn-CH/url", Language: "zn" })
 ```
 
+> NOTE: You can pass the `force` option to override existing content in the path. This is particularly useful for domain alias redirects. See the Netlify documentation on this option [here](https://www.netlify.com/docs/redirects/#structured-configuration).
+
 You can also create a `_redirects` file in the `static` folder for the same effect. Any programmatically created redirects will be appended to the file.
 
 ```sh

Diff for: packages/gatsby-plugin-netlify/src/create-redirects.js

@@ -19,16 +19,21 @@ export default async function writeRedirectsFile(
       fromPath,
       isPermanent,
       redirectInBrowser, // eslint-disable-line no-unused-vars
+      force,
       toPath,
       ...rest
     } = redirect
 
+    let status = isPermanent ? `301` : `302`
+
+    if (force) status = status.concat(`!`)
+
     // The order of the first 3 parameters is significant.
     // The order for rest params (key-value pairs) is arbitrary.
     const pieces = [
       fromPath,
       toPath,
-      isPermanent ? 301 : 302, // Status
+      status,
     ]
 
     for (let key in rest) {