style: code formatting and checks in the CI
### New Pull Request Checklist
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- [x] I am not disclosing a [vulnerability](https://github.com/parse-community/Parse-SDK-Android/blob/master/SECURITY.md).
- [x] I am creating this PR in reference to an [issue](https://github.com/parse-community/Parse-SDK-Android/issues?q=is%3A1119).

### Issue Description

Related issue: #1119 

### Approach
Added Spotless formatter for most types of files in the project (eg. .java, .kt, .xml, .gradle).
Spotless is configured to use ktlint for Kotlin and Google Code Style AOSP for Java.

### TODOs before merging

- [ ] ~~Add tests~~
- [x] Add changes to documentation (guides, repository pages, in-code descriptions)
- [x] A changelog entry is created automatically using the pull request title (do not manually add a changelog entry)

.github/workflows/ci.yml
# For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-gradle

name: ci
on:
  push:
    branches:
      - master
  pull_request:
    branches:
      - '**'
jobs:
  check-build:
    name: Gradle Build
    timeout-minutes: 5
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: Set up JDK 11
        uses: actions/setup-java@v2
        with:
          java-version: '11'
          distribution: 'adopt'
      - name: Validate Gradle wrapper
        uses: gradle/wrapper-validation-action@e6e38bacfdf1a337459f332974bb2327a31aaf4b
      - run: pip install --user codecov
      - run: mkdir "$ANDROID_HOME/licenses" || true
      - run: echo "24333f8a63b6825ea9c5514f83c2829b004d1fee" >> "$ANDROID_HOME/licenses/android-sdk-license"
      - run: ./gradlew clean jacocoTestReport
      - run: codecov
# For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-gradle

name: ci
on:
  push:
    branches:
      - master
  pull_request:
    branches:
      - '**'
jobs:
  check-lint:
    name: Lint
    timeout-minutes: 5
    runs-on: ubuntu-latest
    steps:
      - name: Fetch Sources
        uses: actions/checkout@v2
      - name: Set up JDK 11
        uses: actions/setup-java@v2
        with:
          java-version: '11'
          distribution: 'adopt'
      - name: Setup Gradle Dependencies Cache
        uses: actions/cache@v2
        with:
          path: ~/.gradle/caches
          key: ${{ runner.os }}-gradle-caches-${{ hashFiles('**/*.gradle', '**/*.gradle.kts') }}
      - name: Setup Gradle Wrapper Cache
        uses: actions/cache@v2
        with:
          path: ~/.gradle/wrapper
          key: ${{ runner.os }}-gradle-wrapper-${{ hashFiles('**/gradle/wrapper/gradle-wrapper.properties') }}
      - name: Spotless check
        run: ./gradlew spotlessCheck --no-daemon
  check-gradlewrapper:
    name: Gradle Wrapper
    timeout-minutes: 5
    runs-on: ubuntu-latest
    steps:
      - name: Fetch Sources
        uses: actions/checkout@v2
      - name: Gradle Wrapper Validation
        uses: gradle/wrapper-validation-action@v1
  check-build:
    name: Gradle Build
    timeout-minutes: 15
    runs-on: ubuntu-latest
    steps:
      - name: Fetch Sources
        uses: actions/checkout@v2
      - name: Set up JDK 11
        uses: actions/setup-java@v2
        with:
          java-version: '11'
          distribution: 'adopt'
      - name: Setup Gradle Dependencies Cache
        uses: actions/cache@v2
        with:
          path: ~/.gradle/caches
          key: ${{ runner.os }}-gradle-caches-${{ hashFiles('**/*.gradle', '**/*.gradle.kts') }}
      - name: Setup Gradle Wrapper Cache
        uses: actions/cache@v2
        with:
          path: ~/.gradle/wrapper
          key: ${{ runner.os }}-gradle-wrapper-${{ hashFiles('**/gradle/wrapper/gradle-wrapper.properties') }}
      - name: Run tests
        run: ./gradlew --no-daemon clean jacocoTestReport
      - name: Report test coverage
        run: |
          pip install --user codecov
          codecov

Sorry, maybe I should clarify: the license line is currently part of the CI, but this PR removes the license line. So I wonder whether we really want to remove it and what possible effect this could have.