chore(build) version upgrades: Gradle 6.0.1 -->> 9.1.0; spotless gradle plugin: 3.27.0 -->> 8.0.0

details about changes and solved issues:
 - warning: `'indentWithTabs' is deprecated, use 'leadingSpacesToTabs' in your gradle build script instead`: diffplug/spotless#794 (comment)
 - error: `Spotless failure, no target set!  You must set a target for freshmark`: (https://github.com/diffplug/spotless/tree/gradle/8.0.0/plugin-gradle#freshmark)

Author: dejan2609

.gitignore

@@ -14,3 +14,6 @@ bin/
 
 # Matlab stuff
 .m~
+
+# IntelliJ Idea
+.idea

README.md

@@ -24,4 +24,3 @@ I put all my blog posts here so that I can run CI on the code examples, and make
 * [A library by any other version](https://github.com/diffplug/blog/tree/master/2015/a-library-by-any-other-version) (May 15, 2015)
 * [A new formatting plugin](https://github.com/diffplug/blog/tree/master/2015/a-new-formatting-plugin) (May 13, 2015)
 * [All of heartbleed](https://github.com/diffplug/blog/tree/master/2014/all-of-heartbleed) (April 11, 2014)
-

build.gradle

@@ -1,5 +1,9 @@
 plugins {
-	id "com.diffplug.gradle.spotless" version "3.27.0"
+	id "com.diffplug.spotless" version "8.0.0"
+}
+
+repositories {
+	mavenCentral()
 }
 
 ////////////
@@ -23,11 +27,12 @@ spotless {
 	}
 	format 'misc', {
 		target '**/.gitignore', '**/*.gradle', '**/*.md', '**/*.sh'
-		indentWithTabs()
+		leadingSpacesToTabs()
 		trimTrailingWhitespace()
 		endWithNewline()
 	}
 	freshmark {
+		target '*.md'
 		properties {
 			it.put('follow', FOLLOW_LINK)
 		}

gradle/wrapper/gradle-wrapper.jar

@@ -1,6 +1,8 @@
-#Fri Jan 03 01:08:08 PST 2020
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
+distributionSha256Sum=a17ddd85a26b6a7f5ddb71ff8b05fc5104c0202c6e64782429790c933686c806
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.1.0-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.0.1-bin.zip