Updated badges and documentation.

* Fixed the badging of `Build Status` and `Codecov`.
* Since there is no `master` and `develop` branches, we have updated our `CONTRIBUTING.md` to reflect these changes.

CONTRIBUTING.md

@@ -32,7 +32,7 @@ Our process for accepting changes operates by [Pull Request (PR)](https://help.g
 
 1.  **Create or modify the files** with your changes. If you want to show other people work that isn't ready to merge in, commit your changes then create a pull request (PR) with _WIP_ or _Work In Progress_ in the title.
 
-        https://github.com/kiwix/<repository-name>/pull/new/master
+        https://github.com/kiwix/<repository-name>/pull/new/main
 
 1.  Once your changes are ready for final review, commit your changes then modify or **create your pull request (PR)**, assign as a reviewer or ping (using "`@<username>`") a Lieutenant (someone able to merge in PRs) active on the project (all Lieutenants can be pinged via `@kiwix/lieutenants`)
 
@@ -44,10 +44,9 @@ Our process for accepting changes operates by [Pull Request (PR)](https://help.g
 
 Our branching strategy is based on [this article](https://nvie.com/posts/a-successful-git-branching-model/) which we suggest you read.
 
-+ **master** a history of releases, once merged to from develop and tagged we create a release on the play store & GitHub releases.
-+ **develop**  the actively worked on next release of the app, what we branch off of while working on new features and what we merge into upon feature completion
++ **main**  the actively worked on next release of the app, what we branch off of while working on new features and what we merge into upon feature completion
 + **feature/** or feature/\<username\>/ any branch under this directory is an actively developed feature, feature branches culminate in a PR, are merged and deleted.
- Typically a feature branch is off of develop and into develop but in rare scenarios if there is an issue in production a branch may be made off master to fix this issue, this type of feature branch must be merged to develop and master before being deleted.
+ Typically a feature branch is off of main and into develop but in rare scenarios if there is an issue in production a branch may be made off main to fix this issue, this type of feature branch must be merged to main before being deleted.
 Branch names should be in the format **\<issue-number\>-kebab-case-title**
 
 All branches should have distinct history and should be visually easy to follow, for this reason only perform merge commits when merging code either by PR or when synchronising.

README.md

@@ -39,9 +39,9 @@ website to access the complete set of features.
 
 Kiwix Android is written in [Kotlin](https://kotlinlang.org/)
 
-[![Build Status](https://github.com/kiwix/kiwix-android/workflows/CI/badge.svg?query=branch%3Adevelop+workflow%3ANightly)](https://github.com/kiwix/kiwix-android/actions?query=workflow%3ACI+branch%3Amain)
+[![Build Status](https://github.com/kiwix/kiwix-android/workflows/CI/badge.svg?query=branch%3Amain+workflow%3ANightly)](https://github.com/kiwix/kiwix-android/actions?query=workflow%3ACI+branch%3Amain)
 [![Nightly](https://github.com/kiwix/kiwix-android/actions/workflows/nightly.yml/badge.svg)](https://github.com/kiwix/kiwix-android/actions/workflows/nightly.yml)
-[![codecov](https://codecov.io/gh/kiwix/kiwix-android/branch/develop/graph/badge.svg)](https://codecov.io/gh/kiwix/kiwix-android)
+[![codecov](https://codecov.io/gh/kiwix/kiwix-android/branch/main/graph/badge.svg)](https://codecov.io/gh/kiwix/kiwix-android)
 [![CodeFactor](https://www.codefactor.io/repository/github/kiwix/kiwix-android/badge)](https://www.codefactor.io/repository/github/kiwix/kiwix-android)
 [![License: GPL v3](https://img.shields.io/badge/License-GPLv3-blue.svg)](https://www.gnu.org/licenses/gpl-3.0)
 [![Public Chat](https://img.shields.io/badge/public-chat-green)](https://chat.kiwix.org)