Multiple enhancements and bugfixes

!Breaking change! - The updated version will not be able to read your old database file

Major improvements:
- Added editable pastas
- Added private pastas
- Added line numbers
- Added support for wide mode (1080p instead of 720p)
- Added syntax highlighting support
- Added read-only mode
- Added built-in help page
- Added option to remove logo, change title and footer text

Minor improvements:
- Improved looks in pure html mode
- Removed link to GitHub repo from navbar
- Broke up 7km long main.rs file into smaller modules
- Moved water.css into a template instead of serving it as an external resource
- Made Save button a bit bigger
- Updated README.MD

Bugfixes:
- Fixed a bug where an incorrect animal ID in a request would cause a crash
- Fixed a bug where an empty or corrupt JSON database would cause a crash

src/endpoints/errors.rs

@@ -0,0 +1,16 @@
+use actix_web::{Error, HttpResponse};
+use askama::Template;
+
+use crate::args::{Args, ARGS};
+
+#[derive(Template)]
+#[template(path = "error.html")]
+pub struct ErrorTemplate<'a> {
+    pub args: &'a Args,
+}
+
+pub async fn not_found() -> Result<HttpResponse, Error> {
+    Ok(HttpResponse::Found()
+        .content_type("text/html")
+        .body(ErrorTemplate { args: &ARGS }.render().unwrap()))
+}