polish elapsed time

Author: jiacai2050

src/03-01-elapsed-time.md

@@ -1,6 +1,6 @@
 ### Measure the elapsed time between two code sections
 
-Measures [`std.time.Instant.since`] since [`std.time.Instant.now`].
+[`Instant`] represents a timestamp with respect to the currently executing program that ticks during suspend and can be used to record elapsed time.
 
 Calling [`std.time.Instant.since`] returns a u64 representing nanoseconds elapsed.
 
@@ -27,8 +27,5 @@ pub fn main() !void {
 }
 ```
 
-[`std.time.ns_per_s`]: https://ziglang.org/documentation/master/std/#A;std:time.ns_per_s
+[`Instant`]: https://ziglang.org/documentation/master/std/#A;std:time.Instant
 [`std.time.Instant.since`]: https://ziglang.org/documentation/master/std/#A;std:time.Instant.since
-[`std.time.Instant.now`]: https://ziglang.org/documentation/master/std/#A;std:time.Instant.now
-[`std.time.Instant`]:https://ziglang.org/documentation/master/std/#A;std:time.Instant
- Measure the elapsed time

src/intro.md

@@ -5,15 +5,17 @@
 
 [Zig cookbook](https://zigcc.github.io/zig-cookbook/) is a collection of simple Zig programs that demonstrate good practices to accomplish common programming tasks.
 
-# How to run
+# How to use
+
+[The website](https://zigcc.github.io/zig-cookbook/) is generated by [mdbook](https://rust-lang.github.io/mdBook/), `mdbook serve` will start a server at `http://localhost:3000` for preview.
 
 Each recipe is accompanied by an illustrative example named after its corresponding sequence number. These examples can be executed using the command `zig build run-{chapter-num}-{sequence-num}`, or `zig build run-all` to execute all.
 
 > Currently Zig 0.11.0 is required to run those examples.
 
 # Contributing
 
-This cookbook is a work in progress, and we welcome contributions from the community. If you have a favorite recipe that you'd like to share, please submit a pull request.
+This cookbook is a work in progress, and we welcome contributions from the community. If you have a favorite recipe that you'd like to share, please submit a [pull request](https://github.com/zigcc/zig-cookbook/pulls).
 
 # Acknowledgment