Add ability for CLI to recognize plaintext BED files

[cmdcolin]

This just adds a small adapter to recognize BED files to the CLI, using BedAdapter

[codecov]

Codecov Report

Merging #3173 (e337ba8) into main (7ed81c2) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main    #3173      +/-   ##
==========================================
- Coverage   59.45%   59.44%   -0.02%     
==========================================
  Files         671      671              
  Lines       28628    28630       +2     
  Branches     6926     6927       +1     
==========================================
- Hits        17022    17020       -2     
- Misses      11284    11288       +4     
  Partials      322      322              

Impacted Files	Coverage Δ
products/jbrowse-cli/src/commands/add-track.ts	62.21% <0.00%> (-0.58%)	⬇️
products/jbrowse-cli/src/types/common.ts	72.50% <ø> (ø)
plugins/hic/src/HicRenderer/HicRenderer.tsx	95.45% <0.00%> (-4.55%)	⬇️
products/jbrowse-web/src/util.ts	48.33% <0.00%> (ø)

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