Flipper Release: v0.21.0

Summary:
# Highlights

- Revamped documentation! We redesigned https://fbflipper.com/ and hope you like it. We added new tutorials, feature pages and way too many things to list here.
- `no-op` package for Android makes it easier to (not) ship Flipper with production releases.
- "Copy as cURL" support for the network plugin (https://github.com/facebook/flipper/pull/415)

Reviewed By: danielbuechele

Differential Revision: D15518400

fbshipit-source-id: 041cc546f4bfd70b13d9bb25eaa6eecf5dc1d7f9

docs/getting-started.md

@@ -50,10 +50,10 @@ repositories {
 }
 
 dependencies {
-  debugImplementation 'com.facebook.flipper:flipper:0.20.3'
+  debugImplementation 'com.facebook.flipper:flipper:0.21.0'
   debugImplementation 'com.facebook.soloader:soloader:0.5.1'
 
-  releaseImplementation 'com.facebook.flipper:flipper-noop:0.20.0'
+  releaseImplementation 'com.facebook.flipper:flipper-noop:0.21.0'
 }
 ```
 
@@ -108,7 +108,7 @@ We support both Swift and Objective-C for Flipper with CocoaPods as build and di
 ```ruby
 project 'MyApp.xcodeproj'
 swift_version = "4.1"
-flipperkit_version = '0.20.3'
+flipperkit_version = '0.21.0'
 
 target 'MyApp' do
   platform :ios, '9.0'
@@ -140,7 +140,7 @@ end
 ```ruby
 project 'MyApp.xcodeproj'
 swift_version = "4.1"
-flipperkit_version = '0.20.3'
+flipperkit_version = '0.21.0'
 
 target 'MyApp' do
   platform :ios, '9.0'