change upper case to lower cas in fragment ids (#7020)

note- caps are ok in hex-escaped fragments

books/free-programming-books-az.md

@@ -3,7 +3,7 @@
 * [C](#c)
 * [HTML and CSS](#html-and-css)
 * [JavaScript](#javascript)
-* [Linux](#Linux)
+* [Linux](#linux)
 * [PHP](#php)
 
 

books/free-programming-books-fr.md

@@ -46,7 +46,7 @@
 * [SPIP](#spip)
 * [SQL](#sql)
 * [Systèmes d'exploitation](#systemes-d-exploitation)
-* [TEI](#TEI)
+* [TEI](#tei)
 * [Vim](#vim)
 
 

books/free-programming-books-ko.md

@@ -2,7 +2,7 @@
 
 * [Amazon Web Service](#amazon-web-service)
 * [Assembly Language](#assembly-language)
-* [AWK](#AWK)
+* [AWK](#awk)
 * [C](#c)
 * [C++](#cpp)
 * [Docker](#docker)
@@ -29,9 +29,9 @@
 * [Ruby](#ruby)
 * [Rust](#rust)
 * [Scratch](#scratch)
-* [Sed](#Sed)
+* [Sed](#sed)
 * [Software Engineering](#software-engineering)
-* [Springboot](#Springboot)
+* [Springboot](#springboot)
 * [Unicode](#unicode)
 
 

books/free-programming-books-ta.md

@@ -1,14 +1,14 @@
 ## Index
 
-* [Big Data](#BigData)
+* [Big Data](#bigdata)
-* [Database](#Database)
+* [Database](#database)
 * [HTML and CSS](#html-and-css)
-* [JavaScript](#Javascript)
+* [JavaScript](#javascript)
-* [Machine Learning](#MachineLearning)
+* [Machine Learning](#machine-learning)
-* [MySQL](#MySQL)
+* [MySQL](#mysql)
-* [PHP](#PHP)
+* [PHP](#php)
-* [Ruby](#Ruby)
+* [Ruby](#ruby)
-* [Selenium](#Selenium)
+* [Selenium](#selenium)
 
 
 ### BigData

courses/free-courses-ru.md

@@ -17,7 +17,7 @@
 * [PHP](#php)
 * [PostgreSQL](#postgresql)
 * [Python](#python)
-* [R](#R)
+* [R](#r)
 * [Ruby](#ruby)
 
 

more/free-programming-cheatsheets.md

@@ -20,7 +20,7 @@
     * [Nuxt.js](#nuxtjs)
     * [React.js](#reactjs)
     * [Vue.js](#vuejs)
-* [Kotlin](#Kotlin)
+* [Kotlin](#kotlin)
 * [Kubernetes](#kubernetes)
 * [Language Translations](#language-translations)
 * [Markdown](#markdown)