[DO NOT MERGE] Modify tutorial to reflect isolated development mode.

[freakboy3742]

NOTE: This should not be merged until Briefcase 0.4 is released.

beeware/briefcase#2593 modified how briefcase dev interacts with requirements. This means some very slightly different output on first run of briefcase dev, and a change to tutorial 7 - users can't pip install faker; they have to add it to requires and run briefcase dev -r. This content mostly existed already, as it was needed for briefcase update -r; but now need that explanation sooner.

beeware/briefcase#2592 also provides a better experience for missing system dependencies on Linux, which we can signpost at the appropriate points.

This updates the tutorial to reflect these changes.

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct

[mhsmith]

Is this actually what the environment would be called? The other platforms say cpython rather than cp, and the wheel tag is win_amd64 rather than win32.

Likewise for the other examples in the tutorial.

[freakboy3742]

Yes. The naming is derived from the binary wheel extension on the platform. If you've got a 64-bit Intel build of Python, this is what the platform-identifying part of the binary wheel looks like. You can confirm this with binary wheels (e.g., the -cp313-cp313-win_arm64.whl wheel for Pillow contains PIL/_imaging.cp313-win_arm64.pyd.

[mhsmith]

Actually the naming is derived from importlib.machinery.EXTENSION_SUFFIXES[0], which isn't the same as the wheel tag in general. Based on my tests, for some reason they're not consistent about cpython vs cp. So the examples are all correct, except that it should be win_amd64, not win32_amd64.

[mhsmith]

Also, there are some spelling errors in the RTD build.

[freakboy3742]

Also, there are some spelling errors in the RTD build.

🤦 Clearly I forgot to run lint before pushing.

I've applied your suggestions manually (GitHub GUI was having issues with some of them because they were on "deleted lines"?), and corrected those spelling issues.