(deps) Add regex crate and improve MIME type detection

- Added `regex` dependency to obiread crate
- Replaced manual byte checks with regex-based detection for FASTA/FASTQ formats in mimetype.rs
- Switched from `once_cell::sync::Lazy` to standard library's `std:: sync :: LazyLock`
- Added generic text/plain fallback detection for ASCII-compatible content
- Updated `MimeTypeGuesser::new` constructor call syntax and simplified API usage of PeekReader's header method
- Implemented `Read trait for MimeTypeGuesser to allow transparent passthrough reading

src/Cargo.lock

@@ -706,6 +706,7 @@ dependencies = [
  "infer",
  "niffler",
  "obikrope",
+ "regex",
  "tracing",
  "tracing-subscriber",
  "ureq",
@@ -815,6 +816,18 @@ dependencies = [
  "crossbeam-utils",
 ]
 
+[[package]]
+name = "regex"
+version = "1.12.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e10754a14b9137dd7b1e3e5b0493cc9171fdd105e0ab477f51b72e7f3ac0e276"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-automata",
+ "regex-syntax",
+]
+
 [[package]]
 name = "regex-automata"
 version = "0.4.14"