Egui text input

[Kryptos-FR]

Implement UI.TextInput (single line for now).

It supports having a mutable or immutable initial value. In case a non-existing variable is given, it will expose it.

;; const string
(UI.TextInput "You can't edit this!")

;; immutable variable
"Hello World!" = .imm
(UI.TextInput .imm)

;; mutable variable
"Lorem ipsum" >= .mut
(UI.TextInput .mut)

;; exposing a new string variable
(UI.TextInput .new)

Manipulating the dyn TextBuffer is optimized to only clone when the string capacity is not sufficient. Otherwise it does pointer arithmetic to move slices of memory around.

[codecov]

Codecov Report

Merging #312 (722dcdb) into devel (7e94ecf) will decrease coverage by 31.14%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##            devel     #312       +/-   ##
===========================================
- Coverage   76.37%   45.22%   -31.15%     
===========================================
  Files         155      154        -1     
  Lines       25846    24805     -1041     
===========================================
- Hits        19739    11218     -8521     
- Misses       6107    13587     +7480     

Impacted Files	Coverage Δ
src/core/shards/ShaderFastMathLib.h	0.00% <0.00%> (-100.00%)	⬇️
src/core/shards/reflection.cpp	14.28% <0.00%> (-85.72%)	⬇️
src/core/edn/print.hpp	0.00% <0.00%> (-82.54%)	⬇️
src/extra/snappy.cpp	16.66% <0.00%> (-77.78%)	⬇️
src/extra/dsp.cpp	14.75% <0.00%> (-72.96%)	⬇️
src/extra/brotli.cpp	23.52% <0.00%> (-70.59%)	⬇️
src/core/shards/bigint.cpp	25.09% <0.00%> (-70.52%)	⬇️
src/core/shards/time.cpp	15.71% <0.00%> (-70.00%)	⬇️
src/core/shards/channels.cpp	14.71% <0.00%> (-68.40%)	⬇️
include/ops.hpp	22.67% <0.00%> (-66.76%)	⬇️
... and 49 more

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[guusw]

Minor notes/questions. otherwise looks good.