feat: sign and verify messages

[faustbrian]

Implement message signing and verification.

What kind of change does this PR introduce?

• Bugfix
• Feature
• Refactor
• Performance
• Tests
• Build
• Documentation
• Code style update
• Continuous Integration
• Other, please describe:

Does this PR introduce a breaking change?

• Yes
• No

Does this PR release a new version?

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• It's submitted to the develop branch, not the master branch
• All tests are passing
• New/updated tests are included

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

[codecov-io]

Codecov Report

Merging #25 into master will increase coverage by 5.39%.
The diff coverage is 72.72%.

@@            Coverage Diff            @@
##           master     #25      +/-   ##
=========================================
+ Coverage    31.5%   36.9%   +5.39%     
=========================================
  Files           5       6       +1     
  Lines          73      84      +11     
  Branches        3       3              
=========================================
+ Hits           23      31       +8     
- Misses         50      53       +3

Impacted Files	Coverage Δ
src/crypto.ts	0% <ø> (ø)	⬆️
src/router.ts	0% <0%> (ø)	⬆️
src/message.ts	100% <100%> (ø)

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[ItsANameToo]

TODO:

• responsiveness
• homepage button solution; e.g. toggle or something similar

[ItsANameToo]

@faustbrian take a look