Added DBMS Cheatsheet PDF, Contributed Statistics Book, and New Resource in Programming Books List

[Omsongire23]

What does this PR do?
Add resource(s) | Add info

Issue : #11629
#11259
For resources
#11225
#Dcription
Added a DBMS Cheatsheet PDF and provided a link to the file in the README.md also contibute the Statistics book in free-courses-en.md and add a resource in free-programming-en.md

#Why is this valuable (or not)?

1. The DBMS cheatsheet provides a quick reference guide to important SQL commands, which is useful for students or developers working with databases.
2. The Statistics book contributes free, quality educational content to the statistics section, helping learners understand core statistical concepts.
3. The new resource added to free-programming-books-en.md expands the list of freely available programming books, providing more learning opportunities for the community.

#How do we know it's really free?
The DBMS Cheatsheet is a free resource hosted in the repository, openly available for users to download and on other hand the Statistics book and the resource in free-programming-books-en.md have been verified to be free and accessible without paywalls or subscription requirements.

#For book lists, is it a book? For course lists, is it a course? etc.
DBMS Cheatsheet: This is a PDF cheatsheet for SQL.
Statistics book: This is a free online book on Statistics.
The resource added in free-programming-books-en.md is a free programming book.

#Checklist:

• Read our contributing guidelines.
• Search for duplicates.
• Include author(s) and platform where appropriate.
• Put lists in alphabetical order, correct spacing.
• Add needed indications (PDF, access notes, under construction).
• Used an informative name for this pull request.

[github-actions]

Linter failed, fix the error(s):

free-programming-books/books/free-programming-books-langs.md
1588:1-1593:207  warning  Alphabetical ordering: swap l.1593 and l.1592  alphabetize-lists  remark-lint
1593:3-1593:207  warning  Missing PDF indication                         books-links        remark-lint

free-programming-books/courses/free-courses-en.md
522:1-556:129  warning  Alphabetical ordering: swap l.525 and l.524  alphabetize-lists  remark-lint
524:3-524:224  warning  Missing PDF indication                       books-links        remark-lint

free-programming-books/more/free-programming-cheatsheets.md
    3:1-64:22  warning  Alphabetical ordering: swap l.14 and l.13                              alphabetize-lists  remark-lint
    3:1-64:22  warning  Alphabetical ordering: swap l.15 and l.14                              alphabetize-lists  remark-lint
141:1-146:143  warning  Incorrect number of blank lines between last section and next heading  blank-lines-1-0-2  remark-lint
 150:1-150:90  warning  Incorrect number of blank lines between last section and next heading  blank-lines-1-0-2  remark-lint
 150:3-150:90  warning  Missing PDF indication                                                 books-links        remark-lint

[github-actions]

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