Private blockchain - Add custom network / add custom token by QR code

#Description
As a customer, I want user-friendly way how to add private network and toknes on that network

#Situation
Company will emit some tokens on theirs private ethereum blockchain and want their customers to use those tokens as some kind of "credit" system. Company want for their customers make process as-easy-possible.

For now they use QR code with HTML page with Javascript based code, which uses ethereum API to add custom network and custom tokens. But this solution does not meets company project manager, because 1) there is extra window which complains about "going to external link" and 2) after web page is opened in internal metamask browser, token is added, this window remains opened.

**Acceptance Criteria**
Network add
1. Company will make public QR code with custom network details and QR code with their Tokens on that private network
2. Customer / User of metamask will open metamask, open QR code reader
3. Customer read Custom network details
4. Metamask will ADD this custom network without any abusing windows like "opening external window" or remain on some other page. There will be only information like "Add custom network ?"

Token add
1. Company will make public or send QR code to customer with token details
2. Customer/user will scan this QR with metamask QR code scanner
3. Metamask will ask about add this token, without any extra dialogs like "visition external web site" or "remain on opened page"

Is there already something what can achieve this scenario ?

**Process** (adapt per story)
- [ ] User research / data
- [ ] Ideation / Kickoff in cross-functional team
- [ ] Pattern research in mobile (crypto / non-crypto space)
- [ ] Proof of concept to check technical feasibility (if applicable)
- [ ] Design reviews with PM, Engineer(s)
- [ ] User testing
- [ ] Design - Dev handoff
- [ ] Implementation
- [ ] Code review
- [ ] Stakeholder review on latest build on iOS and Android
- [ ] QA - unit test, e2e tests, regression testing

Start by reviewing the existing MetaMask QR code scanner and the Ethereum API flow described in the issue, then assess whether they can handle custom network and token details directly. A proof of concept should confirm that scanning each QR code leads to an in-app confirmation without opening an external page or leaving a browser window open.

Written by the indexing model from the issue text.