feat: update android guide and example

[ferdicus]

Description

Updates android install guide and /example projects build.gradle

Additional Info

People always come up to me and ask "ferdicus, how can I install custom version of mapbox" or they yell "yo, how to mapLibre" across the street.
Thought it would be a good idea to clean up the android install guide and add example install configs to the ... /example... app.

And here we are.

Checklist

• I have tested this on a device/simulator for each compatible OS
  • tested with default project dependencies
  • tested with up to date mapbox dependencies as commented out within /example > build.gradle
  • tested with mapLibre dependencies as included within /example > build.gradle
• I mentioned this change in CHANGELOG.md

not applicable tests

• I formatted JS and TS files with running yarn lint:fix in the root folder
• I updated the documentation with running yarn generate in the root folder
• I updated the typings files (index.d.ts)
• I added/ updated a sample (/example)

[lisabaut]

LGTM