feat: make both crypto implementations support sign

[alexander-fenster]

We actually don't really need it for now since the JWT code uses jws/jwa to sign the authentication token, but since I started digging into this, I just decided to make two crypto implementations be similar in case if we need it later.

• Tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

[codecov]

Codecov Report

Merging #727 into master will decrease coverage by 0.32%.
The diff coverage is 61.53%.

@@            Coverage Diff             @@
##           master     #727      +/-   ##
==========================================
- Coverage   84.69%   84.37%   -0.33%     
==========================================
  Files          18       18              
  Lines         941      947       +6     
  Branches      209      209              
==========================================
+ Hits          797      799       +2     
- Misses         84       88       +4     
  Partials       60       60

Impacted Files	Coverage Δ
src/crypto/crypto.ts	71.42% <ø> (ø)	⬆️
src/crypto/browser/crypto.ts	8.82% <0%> (-1.18%)	⬇️
src/auth/googleauth.ts	86.01% <100%> (-0.12%)	⬇️
src/crypto/node/crypto.ts	100% <100%> (ø)	⬆️

---

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[codecov]

Codecov Report

Merging #727 into master will decrease coverage by 0.32%.
The diff coverage is 61.53%.

@@            Coverage Diff             @@
##           master     #727      +/-   ##
==========================================
- Coverage   84.69%   84.37%   -0.33%     
==========================================
  Files          18       18              
  Lines         941      947       +6     
  Branches      209      209              
==========================================
+ Hits          797      799       +2     
- Misses         84       88       +4     
  Partials       60       60

Impacted Files	Coverage Δ
src/crypto/crypto.ts	71.42% <ø> (ø)	⬆️
src/crypto/browser/crypto.ts	8.82% <0%> (-1.18%)	⬇️
src/auth/googleauth.ts	86.01% <100%> (-0.12%)	⬇️
src/crypto/node/crypto.ts	100% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2fe53ad...abfacc5. Read the comment docs.

[bcoe]

rubber stamp approval, looks reasonable to me.