Docs feedback: Update / fix docs page for "Local development"

[nmrshll]

Here's some small issues I ran into when reading this page of the docs:

1. "iota client envs" / "iota client switch" doesn't seem to work when current env is local AND local network is not running
   • Possible fix: make it possible to switch environment back to “testnet” without having to launch the local network again
   • should I open a separate issues about this ?
2. In section “Install IOTA Wallet Locally” > “Build”:
   • “pnpm turbo build” fails:
     • SOLUTION: list some additional dependencies:
       • nodejs (minimum version to make it work seems to be nodejs_20 now)
       • Rust 1.82+ with target “wasm32-unknown-unknown”
       • docker-compose (+ docker daemon running) (or podman equivalent)
3. In section “Install IOTA Wallet Locally”:
   • missing description of what the IOTA wallet is, what kind of app it is (desktop ? chrome extension only ? CLI ?)
   • what can I do with it once it builds successfully ? Why do I need to build it now ? are we using this in a later section of the docs ?
4. in section “troubleshooting”:
   • min node version is listed as 18, seems to be nodejs 20 now:
     • nodejs_18 fails: Error: tsx must be loaded with --import instead of --loader
     • nodejs_20 works ok
5. in section “Configure the Wallet”
   • iota/apps/wallet/configs/environment/.env.defaults doesn’t seem to exist anymore in the repo. Is it meant to be generated ?
   • is API_ENV=local the only value we need in env for now ? or do the next commands need more values that were previously in .env.defaults ?
   • 12 additional files refer to it and try to load it, should we remove the references to it ?
6. in section “Generate example data”
   • what is this data ? I suppose transactions and objects ? Why do we need it ?
   • where is the section “Prerequisites for Building Apps locally” ? It doesn’t seem to show up in a search
     • possible fix: make the text a link to the section
   • does the command “pnpm --filter @iota/iota-sdk test:e2e” generate this data or run end-to-end tests ? Or does running end-to-end tests generate data that we can later use to write manual tests using the Typescript SDK ?

[nmrshll]

I've opened a draft PR with all the changes I could make so far, some points I still have questions about:
iotaledger/iota#4721
Let's move all the discussion to that pull request.