bug(file_server):clicking filename/dirname makes url absolute path with a 404 code

[yuqingc]

I ran the new file_server example with the --reload flag. There's a bug. When I click one of the file/dir name on the home page, the url becomes the absolute path of my OS, which leads to a 404 of that resource. In line 52 of file_server.ts, the absolute path is passed to the display function, making this error.

[yuqingc]

https://github.com/denoland/deno_std/blob/master/http/file_server.ts#L152

[yuqingc]

Modifying line 165 should work. I have tested. Should I open a PR for that?

From

fn,

to

fn.replace(currentDir, ''),