Add to README info about how to get Apple Developer ID certificate

[rakleed]

Could you add information about how to get Apple Developer ID certificate to the compilation guide for the macOS app? Because I couldn't find a good article about it, although you need to create a certificate in Xcode and then copy ID from Keychain.

[stenya]

Useful links:
https://developer.apple.com/support/developer-id/
https://developer.apple.com/developer-id/

(the text below is copied from: https://help.salesforce.com/s/articleView?id=sf.branded_apps_code_signing_ios.htm&type=5)
Create a Certificate Signing Request
Use Keychain Access on your Mac to create a certificate signing request.

1. From your Mac, launch Keychain Access located in /Applications/Utilities.
2. From the Keychain Access menu in the header, go to Certificate Assistant then select Request a Certificate from a Certificate Authority.
3. Enter your email address in the User Email Address field.
4. Enter a name in the Common Name field.
5. Leave the CA Email Address field blank.
6. Select Saved to disk.
7. Click Continue.

Create Developer ID Certificate
Log into your Apple Developer Account to create and download a Developer ID certificate.

1. Log into your Apple Developer Account and go to Certificates, Identifiers & Profiles.
2. In the upper-left corner, click + to add.
3. Under Software, select Developer ID then click Continue.
4. Click Choose File.
5. Select the certificate request file you created earlier (a file with a certSigningRequest file extension), then click Choose.
6. Click Continue.
7. Click Download.

If promoted, approve the certificate download.

The certificate file (a file with a .cer file extension) is located in your Downloads folder.

Find Your Certificate ID
After creating your Developer ID certificate, locate and save your certificate ID.

Go to the certificate detail page that you created earlier. In the URL, copy and save your certificate ID. In this example URL from a certificate detail page https://developer.apple.com/account/resources/certificates/download/x12345y9876, the certificate ID is x12345y9876