Validate text align

[jkrumbiegel]

Before, you'd get a pretty obscure error when accidentally doing text(..., align = :center)

ERROR: MethodError: no method matching getindex(::Symbol, ::Int64)
The function `getindex` exists, but no method is defined for this combination of argument types.
Stacktrace:
  [1] layout_text(string::String, fontsize::Float32, font::FreeTypeAbstraction.FTFont, fonts::Attributes, align::Symbol, rotation::Quaternion{…}, justification::MakieCore.Automatic, lineheight::Float64, color::ColorTypes.RGBA{…}, strokecolor::ColorTypes.RGBA{…}, strokewidth::Int64, word_wrap_width::Int64)
    @ Makie ~/.julia/dev/Makie/src/layouting/text_layouting.jl:55
  [2] _get_glyphcollection_and_linesegments(str::String, index::Int64, ts::Float32, f::FreeTypeAbstraction.FTFont, fs::Attributes, al::Symbol, rot::Quaternion{…}, jus::MakieCore.Automatic, lh::Float64, col::ColorTypes.RGBA{…}, scol::ColorTypes.RGBA{…}, swi::Int64, www::Int64, offs::Vec{…})
    @ Makie ~/.julia/dev/Makie/src/basic_recipes/text.jl:111
  [3] (::Makie.var"#push_args#2369"{Vector{…}, Vector{…}, Vector{…}, Vector{…}, Vector{…}})(::String, ::Vararg{Any})
    @ Makie ~/.julia/dev/Makie/src/basic_recipes/text.jl:51
  [4] (::Makie.var"#2365#2368"{…})(str::String, ts::Int64, f::Symbol, fs::Attributes, al::Symbol, rot::Float64, jus::MakieCore.Automatic, lh::Float64, cs::Symbol, cmap::Symbol, scol::Tuple{…}, swi::Int64, www::Int64, offs::Tuple{…})
    @ Makie ~/.julia/dev/Makie/src/basic_recipes/text.jl:66
  [5] invokelatest(::Any, ::Any, ::Vararg{Any}; kwargs::@Kwargs{})
    @ Base ./essentials.jl:1055
  [6] invokelatest(::Any, ::Any, ::Vararg{Any})
    @ Base ./essentials.jl:1052
  [7] (::Observables.OnAny)(value::Any)
    @ Observables ~/.julia/packages/Observables/YdEbO/src/Observables.jl:420
  [8] #invokelatest#2
    @ ./essentials.jl:1055 [inlined]
  [9] invokelatest

So I've added more explicit validation. I can't use to_align because that transforms into floats from 0 to 1 and the y component takes :baseline which cannot be converted this way.