Add a list of all relevant formats to the File Formats > Overview page

[Duckwhale]

For people unfamiliar with the file formats used, an introduction should be provided - similar to the README in the old repo.

It should also provide external links to formats that are somewhat relevant but not covered, such as Lua/LUB and image formats.

[Duckwhale]

Such a list can be auto-generated from the GRF archive as well:

# Dump GRF file table to data.grf.json
evo Tools/dump-grf-file-list.lua

# Print file extensions and number of matches (sorted by count)
cat Exports/data.grf.json | grep -o '\.\w\+"' | tr -d '"' | tr -d '.' | sort | uniq -c | sort -n 

Result:

      1 bak
      1 bat
      1 egg
      1 fds
      1 flc
      1 mp3
      1 pptx
      1 rsx
      1 scp
      1 zip
      2 ase
      2 scc
      2 tmp
      3 bson
      3 log
      4 gif
      4 psd
      4 sfk
      4 xml
      5 bik
     16 lua
     21 gr2
     23 fna
     64 db
     91 ezv
    114 txt
    305 imf
    392 jpg
    449 png
    453 lub
    987 gnd
    988 gat
    988 rsw
   1733 rsm2
   2716 str
   3103 wav
   3676 pal
   7048 rsm
   7565 tga
  39505 spr
  46583 bmp
  54845 act