Add support for selecting HTTP version (#38)

Hey, thanks for the helpful library! I am working on
[httpspec](https://github.com/bradcypert/httpspec) and I needed to be
able to set the HTTP version on the curl library. I couldnt find an easy
way to do that without modifying the library, so I went ahead and did
that (and here's a patch to support it!).

---------

Co-authored-by: Jiacai Liu <dev@liujiacai.net>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: 3 people

src/Easy.zig

@@ -20,6 +20,17 @@ timeout_ms: usize,
 user_agent: [:0]const u8,
 ca_bundle: ?ResizableBuffer,
 
+pub const HttpVersion = enum(c_long) {
+    none = c.CURL_HTTP_VERSION_NONE,
+    http1_0 = c.CURL_HTTP_VERSION_1_0,
+    http1_1 = c.CURL_HTTP_VERSION_1_1,
+    http2 = c.CURL_HTTP_VERSION_2_0,
+    http2_tls = c.CURL_HTTP_VERSION_2TLS,
+    http2_prior_knowledge = c.CURL_HTTP_VERSION_2_PRIOR_KNOWLEDGE,
+    http3 = c.CURL_HTTP_VERSION_3,
+    http3_only = c.CURL_HTTP_VERSION_3ONLY,
+};
+
 pub const Method = enum {
     GET,
     POST,
@@ -319,6 +330,14 @@ pub fn setUpload(self: Self, up: *Upload) !void {
     try checkCode(c.curl_easy_setopt(self.handle, c.CURLOPT_READDATA, up));
 }
 
+pub fn setHttpVersion(self: Self, version: HttpVersion) !void {
+    try checkCode(c.curl_easy_setopt(
+        self.handle,
+        c.CURLOPT_HTTP_VERSION,
+        @intFromEnum(version),
+    ));
+}
+
 pub fn setFollowLocation(self: Self, enable: bool) !void {
     const param: c_long = @intCast(@intFromBool(enable));
     try checkCode(c.curl_easy_setopt(self.handle, c.CURLOPT_FOLLOWLOCATION, param));