Add Fee Transparency in the Principles don's and don't section

[pavlenex]

Describe your content request

While reviewing wallets in #493 I noticed that one of the suggestion we commonly make is that wallets need to be clearly transparency on the fees they may be taking from the users.

The only page where we mention transparency is on the principles page, so I'm unsure if this needs to be added in the screens somewhere?

Link to the page

https://bitcoin.design/guide/designing-products/principles/#transparency

Suggestions
Add that wallet developers should be transparent about the fees in the bullet list, don's and don't. Alternatively see if we can update other screens or pages with this important point.

Additional context

Add any other context about the request here.

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[nguyener1]

Here is my copy suggestion. It will be a sub-bullet point for the "Be open and transparent with how your product works" bullet to the "Do's" list under "Transparency" section.

• Be open and transparent with how your product works
  • For wallets, inform the user on all transaction fees beforehand

What do you think?

[pavlenex]

@nguyener1 That's similar to what I was thinking. For example: "Be transparent and inform users on the fees your application charges"

@nguyener1 If you'd like you can do a PR. If you need help, feel free to DM me on Bitcoin Design Slack.