Update to Imagesharp v4 - #60

Prefer comparing 'Length' to 0 rather than using 'Any()', both for clarity and for performance (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1860)

Exception type System.Exception is not sufficiently specific (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca2201)

Use the "Length" property instead of Enumerable.Count() (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1829)

Prefer comparing 'Length' to 0 rather than using 'Any()', both for clarity and for performance (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1860)

Do not guard 'Dictionary.Remove(key)' with 'Dictionary.ContainsKey(key)' (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1853)

Do not declare visible instance fields (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1051)

Do not declare visible instance fields (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1051)

Do not declare visible instance fields (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1051)

Do not declare visible instance fields (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1051)

Do not declare visible instance fields (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1051)