add s3 adapter examples for Linode and Backblaze

_includes/parse-server/file-adapters.md

@@ -175,7 +175,67 @@ var api = new ParseServer({
 
 Don't forget to change **S3_ACCESS_KEY**, **S3_SECRET_KEY** and **S3_BUCKET** to their correct value.
 
-##### S3Adapter constructor options
+### Digital Ocean Spaces
+
+Spaces is an S3-compatible provided by Digital Ocean. It's use the same api as S3 so you can use it with the S3 Adapter.
+You just need to change the AWS Endpoint to point to your Spaces endpoint.
+
+```javascript
+const s3Options = {
+  bucket: "SPACES_BUCKET_NAME",
+  baseUrl: "SPACES_BASE_URL",
+  region: "SPACES_REGION",
+  directAccess: true,
+  globalCacheControl: "public, max-age=31536000",
+  bucketPrefix: "SPACES_BUCKET_PREFIX",
+  s3overrides: {
+    accessKeyId: "SPACES_ACCESS_KEY",
+    secretAccessKey: "SPACES_SECRET_KEY",
+    endpoint: 'SPACES_ENDPOINT'
+  }
+};
+```
+
+### Linode Object Storage
+
+Object Storage is an S3-compatible storage service from Linode. We can configure our S3Adapter to use Linode's service. Please refer to [this guide](https://www.linode.com/docs/guides/how-to-use-object-storage/) for more details on Linode's API.
+
+```js
+const s3Options = {
+  bucket: "S3_BUCKET_NAME",
+  baseUrl: "S3_BASE_URL", // https://myBucket.myRegion.linodeobjects.com
+  region: "S3_REGION", // possible values: eu-central-1 or us-east-1
+  directAccess: false,
+  s3overrides: {
+    accessKeyId: "S3_ACCESS_KEY", // bucket access key
+    secretAccessKey: "S3_SECRET_KEY", // bucket secret key
+    endpoint: "S3_ENDPOINT", // regionName.linodeobjects.com
+  },
+};
+```
+
+### Backblaze
+
+We also can use Backblaze's S3-compatible [B2 Cloud Storage](https://www.backblaze.com/b2/cloud-storage.html) as a storage adapter. Here is a working configuration for B2:
+
+```js
+const s3Options = {
+  bucket: "S3_BUCKET",
+  directAccess: true,
+  baseUrl: "S3_BASE_URL", // taken from BackBlaze, normally https://BUCKET.s3.REGION.backblazeb2.com
+  baseUrlDirect: false,
+  signatureVersion: 'v4',
+  globalCacheControl: 'public, max-age=86400',
+  region: 'us-west-000',
+  s3overrides: {
+    endpoint: "S3_ENDPOINT", // check backblaze bucket endpoint
+    accessKeyId: "S3_ACCESS_KEY",
+    secretAccessKey: "S3_SECRET_KEY"
+  },
+};
+```
+
+#### S3Adapter constructor options
 
 ```js
 new S3Adapter(accessKey, secretKey, bucket, options)
@@ -249,46 +309,6 @@ var api = new ParseServer({
 });
 ```
 
-##### S3Adapter configuration for Digital Ocean Spaces
-
-Spaces is an S3 equivalent prodivided by Digital Ocean. It's use the same api as S3 so you can use it with the S3 Adapter.
-You just need to change the AWS Endpoint to point to your Spaces endpoint.
-
-```javascript
-...
-var S3Adapter = require('parse-server').S3Adapter;
-var AWS = require("aws-sdk");
-
-//Set Digital Ocean Spaces EndPoint
-const spacesEndpoint = new AWS.Endpoint(process.env.SPACES_ENDPOINT);
-//Define S3 options
-var s3Options = {
-  bucket: process.env.SPACES_BUCKET_NAME,
-  baseUrl: process.env.SPACES_BASE_URL,
-  region: process.env.SPACES_REGION,
-  directAccess: true,
-  globalCacheControl: "public, max-age=31536000",
-  bucketPrefix: process.env.SPACES_BUCKET_PREFIX,
-  s3overrides: {
-    accessKeyId: process.env.SPACES_ACCESS_KEY,
-    secretAccessKey: process.env.SPACES_SECRET_KEY,
-    endpoint: spacesEndpoint
-  }
-};
-
-var s3Adapter = new S3Adapter(s3Options);
-
-var api = new ParseServer({
-  databaseURI: databaseUri || 'mongodb://localhost:27017/dev',
-  appId: process.env.APP_ID || 'APPLICATION_ID',
-  masterKey: process.env.MASTER_KEY || 'MASTER_KEY',
-  ...
-  filesAdapter: s3Adapter
-  ...
-});
-```
-
-
 ##### GCSAdapter constructor options
 
 ```js