feat: keep translation text when switching languages

[VVill-ga]

When a user presses the 'swap languages' button, the translated text should be brought over to the input field, as it is relevant to that language.

Before using the TranslateYou app, I had utilized this feature in Google Translate as a quick first check for translation accuracy. For example, if I translated a sentence into one language, hit the swap button and the English sentence was completely different, I knew I probably shouldn't use that translation.

I only added one line of code for this to work on my device, in the onClick function on the translate button, however I don't know the codebase very well, so let me know if there are any issues with directly assigning the input text like this.

Thanks for the great app!

[Bnyro]

Thanks for your PR!

I think we should additionally clear the translated text after it is being copied to the input field?

Otherwise we will have the same text as input and translation while we didn't yet get a translation result response from the used translation engine.