add utf8proc so we can detect unicode char width

pkg/utf8proc/build.zig

@@ -0,0 +1,51 @@
+const std = @import("std");
+
+/// Directories with our includes.
+const root = thisDir() ++ "../../../vendor/utf8proc/";
+const include_path = root;
+
+pub const include_paths = .{include_path};
+
+pub const pkg = std.build.Pkg{
+    .name = "utf8proc",
+    .source = .{ .path = thisDir() ++ "/main.zig" },
+};
+
+fn thisDir() []const u8 {
+    return std.fs.path.dirname(@src().file) orelse ".";
+}
+
+pub fn link(b: *std.build.Builder, step: *std.build.LibExeObjStep) !*std.build.LibExeObjStep {
+    const lib = try buildLib(b, step);
+    step.linkLibrary(lib);
+    step.addIncludePath(include_path);
+    return lib;
+}
+
+pub fn buildLib(
+    b: *std.build.Builder,
+    step: *std.build.LibExeObjStep,
+) !*std.build.LibExeObjStep {
+    const lib = b.addStaticLibrary("utf8proc", null);
+    lib.setTarget(step.target);
+    lib.setBuildMode(step.build_mode);
+
+    // Include
+    lib.addIncludePath(include_path);
+
+    // Link
+    lib.linkLibC();
+
+    // Compile
+    var flags = std.ArrayList([]const u8).init(b.allocator);
+    defer flags.deinit();
+
+    // C files
+    lib.addCSourceFiles(srcs, flags.items);
+
+    return lib;
+}
+
+const srcs = &.{
+    root ++ "utf8proc.c",
+};

pkg/utf8proc/c.zig

@@ -0,0 +1,3 @@
+pub usingnamespace @cImport({
+    @cInclude("utf8proc.h");
+});

pkg/utf8proc/main.zig

@@ -0,0 +1,8 @@
+pub const c = @import("c.zig");
+
+/// Given a codepoint, return a character width analogous to `wcwidth(codepoint)`,
+/// except that a width of 0 is returned for non-printable codepoints
+/// instead of -1 as in `wcwidth`.
+pub fn charwidth(codepoint: u21) u8 {
+    return @intCast(u8, c.utf8proc_charwidth(@intCast(i32, codepoint)));
+}