Replace README.txt with README.md

Patch is working and marking it to RTBC.

Updated with some minor fix.

please review

The patch works fine. Moving it to RTBC

Since the last reviewer does not pay much attention to details, it would be better somebody else reviews the MR.

Reviewed MR!3, the patch is not cleanly applied.

git.drupalcode.org_project_otp_login_-_merge_requests_3.diff.txt:38: trailing whitespace.
Install as usual. See [Installing Drupal Modules](https://www.drupal.org/docs/extending-drupal/installing-modules)
git.drupalcode.org_project_otp_login_-_merge_requests_3.diff.txt:52: trailing whitespace.
          - With `'SMS framework'`, you can use any supported gateway to send
git.drupalcode.org_project_otp_login_-_merge_requests_3.diff.txt:61: trailing whitespace.
         - Note: '`Tiniyo Key (AuthID)`' and '`Tiniyo Secret (AuthSecretID)`'
git.drupalcode.org_project_otp_login_-_merge_requests_3.diff.txt:73: trailing whitespace.
    - Go to '`/admin/structure/block`' and place '`OTP login link`' block to
git.drupalcode.org_project_otp_login_-_merge_requests_3.diff.txt:83: trailing whitespace.
 - Go to '`/admin/config/smsframework/phone_number`' to add phone number
warning: squelched 1 whitespace error
warning: 6 lines add whitespace errors.

2. Change "## Contents of this file" to "## Table of contents".

Hello, I have created a patch for the same please review.

Description of the module is missing.

Hi thakurnishant_06,

I applied the MR !3 it applies but there are whitespace errors:

➜  otp_login git:(6cc9967) curl https://git.drupalcode.org/project/otp_login/-/merge_requests/3.diff | git apply -v
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  8006    0  8006    0     0   8399      0 --:--:-- --:--:-- --:--:--  8463
<stdin>:54: trailing whitespace.
   - With 'SMS framework', you can use any supported gateway to send 
<stdin>:63: trailing whitespace.
   - Note: 'Tiniyo Key (AuthID)' and 'Tiniyo Secret (AuthSecretID)' 
<stdin>:75: trailing whitespace.
- Go to '/admin/structure/block' and place 'OTP login link' block to 
<stdin>:85: trailing whitespace.
 - Go to '/admin/config/smsframework/phone_number`' to add phone number 
<stdin>:89: trailing whitespace.
    - Under 'Field mapping' -> 'Phone number' select 
Checking patch README.md...
Checking patch README.txt...
Applied patch README.md cleanly.
Applied patch README.txt cleanly.

Please look at the screenshot I attached for your reference,

I removed the trailing whitespaces and changed the table of contents heading.
The required parts were already in the README.md.
Sorry for the many commits.
Please review the MR again.

Reviewed MR!3, the file is updated as per the readme.md file template. Hence marking it to RTBC.