String Interpolation

[Walter Bright]

On 10/22/2023 4:32 AM, Arafel wrote:
> At which point it's barely an improvement overs what we can already do:
> 
> ```
> int var = 67; auto s = mixin(i!"whatever $var");
> ```
> 
> I'm not saving even one keypress, and readability isn't that much better either.

If you can make `i` work as a template, why not? I encourage you to give it a 
try and write the template!

I've already worked out the logic for this:

https://github.com/dlang/dmd/pull/15722/files#diff-a556a8e6917dd4042f541bdb19673f96940149ec3d416b0156af4d0e4cc5e4bdR14291

Feel free to turn it into a template, and let's see.