feat(output): auto-open HTML file after scan

[hogo6002]

Added support to automatically open the HTML file in users' default browser after a scan finishes.

Implementing this by using the right open command for each OS (like xdg-open for Linux, start for Windows, and open for macOS). This way, we don't need to bother with setting up a local server because the HTML file is a self-contained static one.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 12 lines in your changes missing coverage. Please review.

Project coverage is 68.96%. Comparing base (5e82cf7) to head (804193b).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/osv-scanner/scan/main.go	0.00%	11 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1412      +/-   ##
==========================================
- Coverage   69.05%   68.96%   -0.10%     
==========================================
  Files         186      186              
  Lines       18237    18274      +37     
==========================================
+ Hits        12593    12602       +9     
- Misses       4965     4988      +23     
- Partials      679      684       +5     

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[hogo6002]

Hmm, thinking a bit more, if we host it on a localhost port, users could potentially use SSH port forwarding to access the website if they are remotely accessing the server. But I don't know how likely this case would be.
ssh -L local_port:destination_server_ip:remote_port ssh_server_hostname

[oliverchang]

Hmm, thinking a bit more, if we host it on a localhost port, users could potentially use SSH port forwarding to access the website if they are remotely accessing the server. But I don't know how likely this case would be. ssh -L local_port:destination_server_ip:remote_port ssh_server_hostname

This is the workflow I typically use whenever I need to inspect a web page generated by some tool (e.g. documentation)