doc: Document the project creation process

[ithinuel]

This is an attempt at clarifying the possible confusion reported by @moritztim.

Fixes #90

[moritztim]

This is great! Assuming you tested these instructions, that should definitely clear it up.

[moritztim]

It looks like you left an unfinished version of your changes in tho. I merged them for you:

Suggested change

	### Using `cargo-generate`
	```sh
	cargo generate --git https://github.com/rp-rs/rp2040-project-template
	```
	Follow the wizard 🪄 and enjoy your new project.
	### Downloading as a zip file or using GitHub's template support
	Once you have a copy of the code apply the following:
	- Remove `debug_probe.md`.
	- Remove the `cargo-generate` directory.
	- Remote/edit `README.md`.
	- If using vscode update `.vscode/launch.json`;
	Else: remove this file.
	- Edit `Cargo.toml` & adjust according to your project (especially its name).
	- Edit `.cargo/config.tml` to select your favorite runner.
	### Downloading this repository as a zip or generating with github's template
	From GitHub's UI, download this repository as a zip file and remove the `cargo-generate` directory.
	### Generate with `cargo-generate`
	### Generate with `cargo-generate`
	```sh
	cargo generate --git https://github.com/rp-rs/rp2040-project-template
	```
	Follow the wizard 🪄 and enjoy your new project.
	### Downloading as a zip file or using GitHub's template support
	From GitHub's UI, download this repository as a zip file and remove the `cargo-generate` directory.
	Once you have a copy of the code apply the following:
	- Remove `debug_probe.md`.
	- Remove the `cargo-generate` directory.
	- Remote/edit `README.md`.
	- If using vscode update `.vscode/launch.json`;
	Else: remove this file.
	- Edit `Cargo.toml` & adjust according to your project (especially its name).
	- Edit `.cargo/config.tml` to select your favorite runner.

[ithinuel]

Oh that's a good catch thank you!

I reworded the intro to the Manual section 👍

[ithinuel]

I didn't "test" following the instructions. They are a human-readable version of the content of https://github.com/rp-rs/rp2040-project-template/blob/main/cargo-generate/remove_rprs.rhai (+/- some less relevant operations).

[moritztim]

lgtm

[9names]

I'd prefer the brief syntax that assumes github hosting, in case folks are typing this out instead of copy-pasting.

Suggested change

	cargo generate --git https://github.com/rp-rs/rp2040-project-template
	cargo generate rp-rs/rp2040-project-template

[9names]

Also we have installation instructions for everything else, but not for cargo generate.