Migrate to declarative plugin declaration from imperative plugin declaration

[bhawesh2002]

Description

Migrate to gradle's declarative plugin declaration from imperative plugin declaration as refrenced in Deprecated imperative apply of Flutter's Gradle plugins

Fixes

289 : BUG: You are applying Flutter's app_plugin_loader Gradle plugin imperatively using the apply script method

Type of change

Modify :

• android\build.gradle,
• android\app\build.gradle
• android\settings.gradle

to migrate to gradle's declarative plugin declaration

• [x] Bug fix (non-breaking change which fixes an issue)
• [x] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] Documentation update

How Has This Been Tested?

1. Tested on flutter version:
2. Tested on android emulator API 34, API 33 and API 31.

No errors were encountered. Please include screenshots below if applicable.

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] Any dependent changes have been merged and published in downstream modules
• [x] I have checked my code and corrected any misspellings

Maintainer Checklist

• [x] closes #289 (Replace xxxx with the GitHub issue number)
• [x] Tag the PR with the appropriate labels

[bhawesh2002]

The Exception: _TypeError (Null check operator used on a null value) is yet to be fixed. The problem is with static double size_56 = 0.068 * Get.width + 0.034 * Get.height; from lib\utils\ui_sizes.dart

[Aarush-Acharya]

Hey @bhawesh2002 this PR is good to merge, will merge once the PR previous to this are resolved

[bhawesh2002]

Yes, I have resolved the issues and it is good to merge

[vrundraval24]

Good work @bhawesh2002 🚀