Update dependencies; move to @xmldom-scoped is-dom-node package

[cjbarth]

Update devDependencies and change is-dom-node to the @xmldom-scoped package.

[codecov]

Codecov Report

Merging #402 (b0ecaeb) into master (6f95f2e) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #402   +/-   ##
=======================================
  Coverage   74.35%   74.35%           
=======================================
  Files           9        9           
  Lines         889      889           
  Branches      236      236           
=======================================
  Hits          661      661           
  Misses        135      135           
  Partials       93       93           

Files	Coverage Δ
src/c14n-canonicalization.ts	52.10% <100.00%> (ø)
src/enveloped-signature.ts	82.60% <100.00%> (ø)
src/exclusive-canonicalization.ts	77.34% <100.00%> (ø)
src/signed-xml.ts	77.08% <100.00%> (ø)
src/utils.ts	85.18% <100.00%> (ø)

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