better header/footer template, add syntax highlighting

Cargo.toml

@@ -11,11 +11,18 @@ repository = "https://github.com/mrmekon/itsy-gitsy"
 readme = "README.md"
 license = "GPL-3.0-or-later"
 
+[features]
+default = ["markdown", "highlight"]
+markdown = ["dep:pulldown-cmark"]
+highlight_fast = ["syntect/default-onig"]
+highlight = ["syntect/default-fancy"]
 
 [dependencies]
 chrono = { version = "0.4.23", features=["clock"] }
 clap = { version="4.0.32", features=["derive"] }
 git2 = "0.15.0"
+pulldown-cmark = { version = "0.9.2", optional = true }
 serde = { version = "1.0.152", features = ["derive"] }
+syntect = { version = "5.0.0", default-features = false, option = true }
 tera = "1.17.1"
 toml = "0.5.10"