Updated targetSDKVersion

[anilshatharashi]

Closes #3189

Updated the targetSdkVersion to API 28 in order to support the app updates.

What has been done to verify that this works as intended?

Ran the application with the latest targeted version and tested, didn't find any problems with that.

Why is this the best possible solution? Were any other approaches considered?

https://developer.android.com/distribute/best-practices/develop/target-sdk.html

How does this change affect users? Describe intentional changes to behavior and behavior that could have accidentally been affected by code changes. In other words, what are the regression risks?

App can be updated/published without any issues

Do we need any specific form for testing your changes? If so, please attach one.

Not really

Does this change require updates to documentation? If so, please file an issue here and include the link below.

No

Before submitting this PR, please make sure you have:

• run ./gradlew checkAll and confirmed all checks still pass OR confirm CircleCI build passes and run ./gradlew connectedDebugAndroidTest locally.
• verified that any code or assets from external sources are properly credited in comments and/or in the about file.
• verified that any new UI elements use theme colors. UI Components Style guidelines

[seadowg]

Hey @anilshatharashi. It looks like this PR contains commits from a previous PR of yours as well (#3268). It probbaly makes sense to:

1. Make sure you master is in sync with this repo's master (with a git reset --hard upstream/master
2. Start a new branch for this PR (git checkout -b target-api)
3. Cherry pick this commit onto that branch (git cherry-pick c99ea6f)

It's better to make PRs from a branch than your fork's master as it's easier to then merge the latest changes in from upstream - you won't end up with merge commits.