Replace README.txt with README.md

Verified the MR!3 tested, got error after applying patch .

git apply 3.diff.txt.patch.txt
3.diff.txt.patch.txt:40: trailing whitespace.
```
warning: 1 line adds whitespace errors.

After applying patch, got the below error:
3.patch:40: trailing whitespace.
```
warning: 1 line adds whitespace errors.

I removed the trailing whitespace. Please review !MR3.

'The supporting organization' section is not required, right? As it's in the module settings already.

Kind regards

Hi Frederikvho

I reviewed MR!3 and in Project name and introduction missing project page and issue queue links for the module. Sample of Project page and Issue queue based on README.md template.

For a full description of the module, visit the
[project page](https://www.drupal.org/project/admin_menu).

Submit bug reports and feature suggestions, or track changes in the
[issue queue](https://www.drupal.org/project/issues/admin_menu).

Thank you

Please review.

Hi nitin_lama

I reviewed your changes and confirmed that you added "project page and issue queue" links but the Project page text is duplicated and it has a colon symbol while in the README.md template there isn't a colon symbol.

For a full description of the module, visit the
[project page](https://www.drupal.org/project/admin_menu).

Submit bug reports and feature suggestions, or track changes in the
[issue queue](https://www.drupal.org/project/issues/admin_menu).

Thank you.

Updated changes suggested in #16. Please review.

Hi sourabhjain

I reviewed your changes and confirmed that it removed the colon symbol and duplicate text of the "Project page". The README.md is following the README.md template.

Thank you.