docs: ✏️ Update README.md (#197)

Author: nikukyugamer

README.md

@@ -1,77 +1,77 @@
-[![Prekin](https://github.com/nikukyugamer/prekin/actions/workflows/config.yml/badge.svg?branch=main)](https://github.com/nikukyugamer/prekin/actions/workflows/config.yml)
-
 # Prekin
 
+[![Prekin](https://github.com/nikukyugamer/prekin/actions/workflows/config.yml/badge.svg?branch=main)](https://github.com/nikukyugamer/prekin/actions/workflows/config.yml)
+
 ## What is Prekin?
 
 ### Naming
 
 - `Prekin` means `PREMIUM FRIDAY`
-  - `kin` means FRIDAY (`kin-yo-bi`) in Japanese
-  - So `PRE`mium `KIN`-yo-bi is `Prekin`
+    - `kin` means FRIDAY (`kin-yo-bi`) in Japanese
+    - So `PRE`mium `KIN`-yo-bi is `Prekin`
 
 ### Webpage
 
 - A webpage by Ministry of Economy, Trade and Industry in Japan
-  - http://www.meti.go.jp/policy/mono_info_service/service/premium-friday/
+    - <http://www.meti.go.jp/policy/mono_info_service/service/premium-friday/>
 - A webpage by Premium Friday Committee
-  - https://premium-friday.com/
+    - <https://web.archive.org/web/20230411145908if_/https://premium-friday.com/>
 
 ## Installation
 
-Add this line to your application's Gemfile:
+Add this line to your application's `Gemfile`:
 
 ```ruby
 gem 'prekin'
 ```
 
 And then execute:
 
-    $ bundle
+```bash
+$ bundle
+```
 
 Or install it yourself as:
 
-    $ gem install prekin
+```bash
+$ gem install prekin
+```
 
 ## Usage
 
 ### 1. require
+
 - `require 'prekin'`
 
 ### 2. call
 
 #### 2-1. Time class
+
 - `Time.local(2020, 10, 30, 0, 0, 0).prekin? #=> true`
 
 #### 2-2. Date class
+
 - `Date.new(2020, 10, 30).prekin? #=> true`
 
 #### 2-3. DateTime class
+
 - `DateTime.new(2020, 10, 30, 0, 0, 0, '+09:00').prekin? #=> true`
 
 #### 2-4. String class
+
 - `'2020/10/30 00:00:00 +09:00'.prekin? #=> true`
 
 #### 2-5. Next Prekin
+
 - `Prekin.next #=> "2020-10-30"`
 - `Prekin.next('2023-12-28') #=> "2023-12-29"`
 - `Prekin.next('2023-12-29') #=> "2023-12-29"`
 - `Prekin.next('2023-12-30') #=> "2024-01-26"`
 
 ## Note
-- This gem overwrites `Time`, `Date`, `DateTime` and `String` class.
-  - So if you use `Time`, `Date`, `DateTime` and `String` class in your code, you should be careful.
-
-## Development
 
-#### 1. bundle install
-- `bundle install`
-
-#### 2. irb
-- `bundle exec irb`
-
-#### 3. require
-- `require 'prekin'`
+- This gem overwrites `Time`, `Date`, `DateTime` and `String` class.
+    - So if you use `Time`, `Date`, `DateTime` and `String` class in your code, you should be careful.
 
 ## License