feat: upgrade flipper to ink!4 (#284)

* feat: upgrade flipper to ink!4

* Update docs/build/wasm/from-zero-to-ink-hero/flipper-contract/flipper.md

* Update docs/build/wasm/from-zero-to-ink-hero/flipper-contract/flipper.md

---------

Co-authored-by: midegdugarova <59020389+midegdugarova@users.noreply.github.com>

docs/build/wasm/from-zero-to-ink-hero/flipper-contract/flipper-contract.md

@@ -16,10 +16,10 @@ This tutorial targets developers with no experience in ink! and a **basic** leve
 - Basic Rust knowledge. [Learn Rust](https://www.rust-lang.org/learn).
 
 ### What will we do?
-In this tutorial we will implement the most basic contract: [Flipper](https://github.com/paritytech/ink/blob/v3.3.0/examples/flipper/lib.rs) in ink!.
+In this tutorial we will implement the most basic contract: [Flipper](https://github.com/paritytech/ink/blob/v4.0.0/examples/flipper/lib.rs) in ink!.
 
 ### What will we use?
-- [ink! 3.3.0](https://github.com/paritytech/ink/tree/v3.3.0)
+- [ink! 4.0.0](https://github.com/paritytech/ink/tree/v4.0.0)
 
 ### What will you learn?
 - Anatomy of an ink! contract

docs/build/wasm/from-zero-to-ink-hero/flipper-contract/flipper.md

@@ -52,16 +52,14 @@ Let’s dive a bit deeper into the project structure:
 ```rust
 #![cfg_attr(not(feature = "std"), no_std)]
 
-use ink_lang as ink;
-
 #[ink::contract]
 mod flipper {
 
     /// Defines the storage of your contract.
     /// Add new fields to the below struct in order
     /// to add new static storage fields to your contract.
     #[ink(storage)]
-			    pub struct Flipper {
+    pub struct Flipper {
         /// Stores a single `bool` value on the storage.
         value: bool,
     }
@@ -104,9 +102,6 @@ mod flipper {
         /// Imports all the definitions from the outer scope so we can use them here.
         use super::*;
 
-        /// Imports `ink_lang` so we can use `#[ink::test]`.
-        use ink_lang as ink;
-
         /// We test if the default constructor does its job.
         #[ink::test]
         fn default_works() {
@@ -162,23 +157,25 @@ mod flipper {
 ```
 
 This annotates a struct that represents the **contract's internal state.** ([details](https://use.ink/macros-attributes/storage)):
+
 ```rust
 #[ink(storage)]
 ```
 
 Storage types:
+
 - Rust primitives types
-    - `bool`
-    - `u{8,16,32,64,128}`
-    - `i{8,16,32,64,128}`
-    - `String`
+  - `bool`
+  - `u{8,16,32,64,128}`
+  - `i{8,16,32,64,128}`
+  - `String`
 - Substrate specific types
-    - `AccountId`
-    - `Balance`
-    - `Hash`
+  - `AccountId`
+  - `Balance`
+  - `Hash`
 - ink! storage type
-    - `Mapping`
-- Custom data Structure [details](https://use.ink/datastructures/custom-datastructure)
+  - `Mapping`
+- Custom data structure [details](https://use.ink/datastructures/custom-datastructure)
 
 This means the contract (Flipper) stores a single `bool` value in storage.
 
@@ -214,7 +211,7 @@ pub fn default() -> Self {
 }
 ```
 
-The following will permit a function to be **publicly dispatchable**, meaning that it will be exposed in the contract interface to the outside world. [For more information](https://use.ink/4.0.0-alpha.1/macros-attributes/message)). Note that all public functions **must** use the `#[ink(message)]` attribute.
+The following will permit a function to be **publicly dispatchable**, meaning that  the function can be called through a message, which is a way for contracts and external accounts to interact with the contract. Find more information [here](https://use.ink/macros-attributes/message)). Note that all public functions **must** use the `#[ink(message)]` attribute.
 
 ```rust
 #[ink(message)]
@@ -238,7 +235,7 @@ pub fn get(&self) -> bool {
 
 ```rust
 impl Flipper {
-       
+
         #[ink(constructor)]
         pub fn new(init_value: bool) -> Self {
             Self { value: init_value }
@@ -299,5 +296,6 @@ impl Flipper {
 
 ### Compile, Deploy and Interact with Contracts
 
+
 Follow this guide to deploy your contract [using Polkadot UI](https://docs.astar.network/docs/build/wasm/tooling/polkadotjs/). Once deployed, you will be able to interact with it.