docs(README.md): fix code block formatting and typos, improve readability and clarity of usage examples

The changes in this commit fix the formatting of code blocks in the README.md file, correct some typos, and improve the readability and clarity of the usage examples for the `randomstring` package. This makes it easier for users to understand how to use the package and its various features.

Author: necmettindev

README.md

@@ -10,9 +10,9 @@ This library assists in generating random strings based on specific characterist
 
 ## Installation
 
-\```bash
+```bash
 go get -u github.com/necmettindev/randomstring
-\```
+```
 
 ## Usage
 
@@ -22,7 +22,7 @@ Below are different scenarios demonstrating how to use the `randomstring` packag
 
 Generate a string of length 10 using the default alphanumeric characters:
 
-\```go
+```go
 package main
 
 import (
@@ -31,49 +31,57 @@ import (
 )
 
 func main() {
-result, \_ := randomstring.GenerateString(randomstring.GenerationOptions{Length: 10})
-fmt.Println(result)
+    opts := randomstring.GenerationOptions{
+        Length: 10,
+    }
+
+    result, _ := randomstring.GenerateStrin(opts)
+
+    fmt.Println(result)
 }
-\```
+```
 
 ### Disabling Features
 
 For instance, to generate a string containing letters only:
 
-\```go
-opts := randomstring.GenerationOptions{
-Length: 10,
-DisableNumeric: true,
-}
-result, \_ := randomstring.GenerateString(opts)
-fmt.Println(result)
-\```
+```go
+    opts := randomstring.GenerationOptions{
+        Length: 10,
+        DisableNumeric: true,
+    }
+
+    result, _ := randomstring.GenerateString(opts)
+    fmt.Println(result)
+```
 
 ### Using Special Characters
 
 Generate a string with enabled special characters:
 
-\```go
-opts := randomstring.GenerationOptions{
-Length: 15,
-EnableSpecialCharacter: true,
-}
-result, \_ := randomstring.GenerateString(opts)
-fmt.Println(result)
-\```
+```go
+    opts := randomstring.GenerationOptions{
+        Length: 15,
+        EnableSpecialCharacter: true,
+    }
+
+    result, _ := randomstring.GenerateString(opts)
+    fmt.Println(result)
+```
 
 ### Using a Custom Character Set
 
 Generate a string with your own custom character set:
 
-\```go
-opts := randomstring.GenerationOptions{
-Length: 12,
-CustomCharset: "abcXYZ789",
-}
-result, \_ := randomstring.GenerateString(opts)
-fmt.Println(result) // Produces a string consisting only of 'a', 'b', 'c', 'X', 'Y', 'Z', '7', '8', '9'.
-\```
+```go
+    opts := randomstring.GenerationOptions{
+        Length: 12,
+        CustomCharset: "abcXYZ789",
+    }
+
+    result, _ := randomstring.GenerateString(opts)
+    fmt.Println(result) // Produces a string consisting only of 'a', 'b', 'c', 'X', 'Y', 'Z', '7', '8', '9'.
+```
 
 ## Contributing