FixedString 2.0.0

[Moth]

[Version 2.0.0 of 
FixedString](https://github.com/Moth-Tolias/fixedstring/releases/tag/v2.0.0), my @safe @nogc nothrow array type, has been released.

This version is mostly compatible with 1.2.0, but the helper 
template `FixedString!"foo"` has been changed to 
`fixedString!"foo"` to comply with the standard D style 
convention. Furthermore, the range api has been totally 
overhauled; in particular, `opIndex()` now returns a range 
(random access, with slicing) rather than a raw slice, and the 
functions `empty()`, `front()`, and `popFront()` have thus been 
removed from the container.

Previously, it was possible to modify out-of-bounds elements with 
`opIndex` if the maximum size of the `FixedString` would allow 
it. This behaviour does not align with that of native dynamic 
arrays, however, so it has been removed. The correct way to 
perform this action is to either use the `~=` operator, or 
alternatively set the length to an appropriate value beforehand.

It is now possible to use FixedString with types that use the 
garbage collector, throw, or have otherwise unsafe behaviour, as 
the element type. This was impossible in 1.x.x as almost every 
function had the `@nogc nothrow pure @safe` attributes applied. 
However, templates in D automatically infer their attributes - 
meaning this restriction was unnecessary. As such, it has been 
lifted.

There have also been a number of fixes.
- `opAssign`, `opOpAssign`, `opEquals`, `concat` and `opBinary` 
all assumed they would only ever be used with the `char` element 
type. This oversight has been fixed.
- `opSlice` is now bounds checked.

And finally, FixedString is now compatible with dip1000.

[repository](https://github.com/Moth-Tolias/fixedstring)
[dub package](https://code.dlang.org/packages/fixedstring/2.0.0)
[documentation](https://fixedstring.dpldocs.info/v2.0.0/fixedstring.html)
[full 
changelog](https://github.com/Moth-Tolias/fixedstring/blob/main/CHANGELOG.md#200---2022-05-22)