Add a home page

[danielemery]

• Gives some basic information about the instance
  • It's name - (a new option)
  • The number of loaded ssh keys
  • The number of loaded PGP keys
  • The version the instance is running
• Plain text only (html and json still reserved to be done in #34 and #33 respectively)

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 90.38462% with 5 lines in your changes missing coverage. Please review.

Project coverage is 93.64%. Comparing base (4caf8da) to head (b9ba528). Report is 3 commits behind head on main.

Files	Patch %	Lines
src/test_helpers.ts	64.28%	5 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #54 +/- ## ========================================== - Coverage 94.23% 93.64% -0.60% ========================================== Files 9 11 +2 Lines 295 346 +51 Branches 42 44 +2 ========================================== + Hits 278 324 +46 - Misses 17 22 +5 ```

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