[doc] add index file

[inkydragon]

fix #5

[codecov]

Codecov Report

Merging #19 (5d05750) into master (42a0b5f) will increase coverage by 0.20%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #19      +/-   ##
==========================================
+ Coverage   97.43%   97.63%   +0.20%     
==========================================
  Files           4        4              
  Lines         117      127      +10     
==========================================
+ Hits          114      124      +10     
  Misses          3        3              

Impacted Files	Coverage Δ
src/ssh_options.jl	100.00% <0.00%> (ø)
src/verify_host.jl	100.00% <0.00%> (ø)
src/ca_roots.jl	90.32% <0.00%> (+1.03%)	⬆️

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[StefanKarpinski]

Many thanks!