Fix cargo clippy issues and add cargo clippy to the ci

[szabgab]

Running cargo clippy on the cloned repository I get a few warnings.

• Should I send a PR to fix those?
• Should I send a PR to add cargo clippy to the CI to alret you when such thing happens again?

warning: you should consider adding a `Default` implementation for `TextPosition`
  --> src/common.rs:19:5
   |
19 | /     pub const fn new() -> Self {
20 | |         Self { row: 0, column: 0 }
21 | |     }
   | |_____^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.92.0/index.html#new_without_default
   = note: `#[warn(clippy::new_without_default)]` on by default
help: try adding this
   |
15 + impl Default for TextPosition {
16 +     fn default() -> Self {
17 +         Self::new()
18 +     }
19 + }
   |

warning: calling .bytes() is very inefficient when data is not in memory
   --> src/util.rs:112:25
    |
112 |         let mut bytes = source.bytes();
    |                         ^^^^^^^^^^^^^^
    |
    = help: consider using `BufReader`
    = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.92.0/index.html#unbuffered_bytes
    = note: `#[warn(clippy::unbuffered_bytes)]` on by default

warning: all variants have the same prefix: `Wrote`
   --> src/writer/emitter.rs:120:1
    |
120 | / enum IndentFlags {
121 | |     WroteNothing,
122 | |     WroteMarkup,
123 | |     WroteText,
124 | | }
    | |_^
    |
    = help: remove the prefixes and use full paths to the variants instead of glob imports
    = help: for further information visit https://rust-lang.github.io/rust-clippy/rust-1.92.0/index.html#enum_variant_names
    = note: `#[warn(clippy::enum_variant_names)]` on by default

warning: `xml` (lib) generated 3 warnings
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.00s

[kornelski]

They're all intentional. You can add allow for all of these.