Schematics, symbols, boards and footprints all get the ability to store
files inside their file structures. File lookups now have a
kicad-embed:// URI to allow various parts of KiCad to refer to files
stored in this manner.
kicad-embed://datasheet.pdf references the file named "datasheet.pdf"
embedded in the document. Embeds are allowed in schematics, boards,
symbols and footprints. Currently supported embeddings are Datasheets,
3D Models and drawingsheets
Fixes https://gitlab.com/kicad/code/kicad/-/issues/6918
Fixes https://gitlab.com/kicad/code/kicad/-/issues/2376
Fixes https://gitlab.com/kicad/code/kicad/-/issues/17827
Found via `codespell -q 3 -S *.po,./thirdparty,./Documentation/changelogs -L aactual,acount,aline,alocation,alog,anormal,anumber,aother,apoints,aparent,aray,ba,busses,dout,einstance,leaded,modul,ontext,ot,overide,serie,te,,tesselate,tesselator,tht`
