docs: readme add download links

README.md

@@ -22,7 +22,7 @@ The project uses `CMake` as building tool.
 
 ## How to use (in Windows)
 
-1. Download and unzip `markdown2html-x.x.x.zip`
+1. Download and unzip `markdown2html-x.x.x.zip` from [this page](https://github.com/zijunhz/markdown2html/releases/latest).
 2. Open `markdown2html.exe` and follow the instruction:
 3. Input Markdown file path: you need to enter the path to your markdown file. This path can be absolute or be relative to the path where the `.exe` locates. ***It is recommended to copy the markdown file into the folder where the exe is located so that you only need to type in the file name of the markdown file.***
 4. Input output file path: this is the same as 3, but it specifies where you wish the output file is.