Change charListToString to use String.Create

[Numpsy]

Just a thought I had after running a run of FSharpLint over one of my projects thought the Visual Studio memory profiler. It's quite trivial in the overall schema of things, but in case anyone is interested.

I noticed that charListToString was creating quite a large number of strings:

And I wondered if String.Create could be used to reduce the number of temporary strings. Doing so got

The actual amounts of memory here are rather small compared to total memory because the strings are tine -

Before

| Method      | Mean    | Error    | StdDev   | Gen0        | Gen1       | Gen2      | Allocated  |
|------------ |--------:|---------:|---------:|------------:|-----------:|----------:|-----------:|
| LintProject | 3.983 s | 0.1033 s | 0.2964 s | 167000.0000 | 22000.0000 | 1000.0000 | 1008.65 MB |

After

| Method      | Mean    | Error    | StdDev   | Gen0        | Gen1       | Gen2      | Allocated  |
|------------ |--------:|---------:|---------:|------------:|-----------:|----------:|-----------:|
| LintProject | 3.916 s | 0.1088 s | 0.3088 s | 167000.0000 | 22000.0000 | 1000.0000 | 1007.31 MB |

But the change is also small so maybe it's still useful.