Add aria2 to tools list (step 2)

[JackBoosY]

1. Add aria2 to the list of tools
2. Add the aria2 path to the cmake parameters.

Requires microsoft/vcpkg#20971 first.

[BillyONeal]

Well I didn't mean to push my suggestions into your branch but when I attempted to push to my demo branch it pushed to your branch instead.

Can you take a look at the changes I submitted, and confirm that you agree with them? Otherwise, feel free to chop my edits off (git push -f) and do something else. Point is though that we should find the aria2 from the system and always return that rather than potentially sending broken values into cmake.

[JackBoosY]

Test result on Linux:

usr@usr:/home/vcpkg# ./vcpkg fetch aria2
/usr/bin/aria2c

Please note apt only provide aria2 version 1.33.1, the user may need to compile and install it manually. @BillyONeal

[BillyONeal]

Thanks for adding the fun fetch!