`tryparse` does not work

Code to test, using Julia 1.6.6 and FixedPointDecimals 0.4.0:

```
julia> using FixedPointDecimals

julia> tryparse(FixedDecimal{Int64,2},"1.5")
ERROR: MethodError: no method matching tryparse(::Type{FixedDecimal{Int64, 2}}, ::String)
Closest candidates are:
tryparse(::Type{Complex{S}}, ::AbstractString) where S<:Real at parse.jl:384
tryparse(::Type{T}, ::AbstractString) where T<:Dates.TimeType at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/Dates/src/parse.jl:288
tryparse(::Type{T}, ::AbstractString, ::Dates.DateFormat) where T<:Dates.TimeType at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.6/Dates/src/parse.jl:288
...
Stacktrace:
[1] top-level scope
@ REPL[2]:1

julia>
```

It might be useful to look at the [base implementation of `parse`](https://github.com/JuliaLang/julia/blob/v1.6.6/base/parse.jl) to fix this