add(error): introduce zterm.Error containing all zterm errors with their corresponding description

src/container.zig

@@ -6,6 +6,7 @@ const Cell = @import("cell.zig");
 const Color = @import("color.zig").Color;
 const Size = @import("size.zig").Size;
 const Style = @import("style.zig");
+const Error = @import("error.zig").Error;
 
 const log = std.log.scoped(.container);
 
@@ -144,7 +145,7 @@ pub const Rectangle = packed struct {
     /// children accordingly without removing the coloring of the `Rectangle`
     fill: Color = .default,
 
-    // NOTE: caller owns `cells` slice and ensures that `cells.len == size.cols * size.rows`
+    // NOTE: caller owns `Cells` slice and ensures that `cells.len == size.cols * size.rows`
     pub fn contents(this: @This(), cells: []Cell, size: Size) void {
         std.debug.assert(cells.len == @as(usize, size.cols) * @as(usize, size.rows));
 
@@ -600,8 +601,8 @@ pub fn Container(comptime Event: type) type {
                         size.rows,
                     });
                     this.size = size;
-                    if (this.properties.fixed_size.cols > 0 and size.cols < this.properties.fixed_size.cols) return error.TooSmall;
-                    if (this.properties.fixed_size.rows > 0 and size.rows < this.properties.fixed_size.rows) return error.TooSmall;
+                    if (this.properties.fixed_size.cols > 0 and size.cols < this.properties.fixed_size.cols) return Error.TooSmall;
+                    if (this.properties.fixed_size.rows > 0 and size.rows < this.properties.fixed_size.rows) return Error.TooSmall;
 
                     try this.element.handle(event);
 
@@ -623,8 +624,8 @@ pub fn Container(comptime Event: type) type {
                     }
                     // check if the available screen is large enough
                     switch (layout.direction) {
-                        .horizontal => if (fixed_size.cols > size.cols) return error.TooSmall,
-                        .vertical => if (fixed_size.rows > size.rows) return error.TooSmall,
+                        .horizontal => if (fixed_size.cols > size.cols) return Error.TooSmall,
+                        .vertical => if (fixed_size.rows > size.rows) return Error.TooSmall,
                     }
                     const sides = this.properties.border.sides;
                     const padding = layout.padding;