[FIX] Hardcoded backdrop opacity on loading component

[reinaldonetof]

Proposed changes

Apply backdrop opacity theme on Loading component. In addition, added a quick animation to show the backdrop opacity.

Issue(s)

Backdrop opacity was fixed for the Light and Dark theme

How to test or reproduce

The best way to test this task is

• Go to a channel
• Write a message
• Get the permalink from that message
• Paste it and send
• Then, when click on the link will appear the Loading

Screenshots

Before	After

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• Improvement (non-breaking change which improves a current function)
• New feature (non-breaking change which adds functionality)
• Documentation update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works (if applicable)
• I have added necessary documentation (if applicable)
• Any dependent changes have been merged and published in downstream modules

Further comments

[diegolmello]

@reinaldonetof I made some changes on 08ccb7d
Can you re-review and make sure I didn't break anything?
Run StatusView tests from detox pls.
Leaving approve anyways.
Thanks.

[diegolmello]

@reinaldonetof Also can you write a proper test plan (testing themes)?

[CLAassistant]

All committers have signed the CLA.