Previously an invalid `Dioxus.toml` file would yield this error when running e.g. `dx serve`:
```
Error: Failed to load `Dioxus.toml` because: Dioxus.toml parse failed
```
This doesn't give any indication why it failed to parse. This commit updates it to include why the parsing failed, e.g.:
```
Error: Failed to load Dioxus config because: Dioxus.toml missing field `name` for key `application` at line 38 column 1
```
I initially had it format the message to include `Dioxus.toml:38:1` to be clickable in some terminals, but the location specified didn't always seem particularly relevant to the actual problem so I left it as-is.
This also fixes what I believe would be an issue on case-sensitive file systems where if `dioxus.toml` existed it would try to read `Dioxus.toml`.
I'm still fairly new to Rust, so the `.as_path()` calls may not be the best way to deal with the fact that the borrow checker wouldn't let me re-use `crate_dir` and `dioxus_conf_file`. I'm open to suggestions!
