Add missing plugins and update gradle instructions

Author: skydoves

README.md

@@ -21,19 +21,18 @@ Supports alpha & brightness slider bar, dialog, and saving & restoring selected
 </p>
 
 ## Including in your project 
-[![Download](https://api.bintray.com/packages/devmagician/maven/colorpickerview/images/download.svg) ](https://bintray.com/devmagician/maven/colorpickerview/_latestVersion)
 [![Maven Central](https://img.shields.io/maven-central/v/com.github.skydoves/colorpickerview.svg?label=Maven%20Central)](https://search.maven.org/search?q=g:%22com.github.skydoves%22%20AND%20a:%22colorpickerview%22)
 [![Jitpack](https://jitpack.io/v/skydoves/ColorPickerView.svg)](https://jitpack.io/#skydoves/ColorPickerView)
 ### Gradle 
 Add below codes to your **root** `build.gradle` file (not your module build.gradle file).
 ```gradle
 allprojects {
     repositories {
-        jcenter()
+        mavenCentral()
     }
 }
 ```
-And add below dependency code to your **module**'s `build.gradle` file.
+And add a dependency code to your **module**'s `build.gradle` file.
 ```gradle
 dependencies {
     implementation "com.github.skydoves:colorpickerview:2.2.2"

app/build.gradle

@@ -38,6 +38,4 @@ dependencies {
   implementation project(":colorpickerview")
 }
 
-tasks.withType(Javadoc).all { enabled = false }
-
 apply from: "$rootDir/spotless.gradle"

colorpickerview/build.gradle

@@ -14,6 +14,7 @@
 
 apply plugin: 'com.android.library'
 apply plugin: 'kotlin-android'
+apply plugin: 'org.jetbrains.dokka'
 apply from: "$rootDir/dependencies.gradle"
 
 android {
@@ -34,6 +35,5 @@ dependencies {
   implementation "androidx.appcompat:appcompat:$versions.androidxAppcompat"
 }
 
-tasks.withType(Javadoc).all { enabled = false }
-
+apply plugin: "com.vanniktech.maven.publish"
 apply from: "$rootDir/spotless.gradle"