Update FileHTTPHandler to support partial range requests

[swhitty]

Updates FileHTTPHandler to support partial range requests.

Routes for both GET and HEAD must be created to a file:

await server.appendRoute("GET,HEAD /jaws", to: .file(named: "jaws.m4v"))

When clients request the route and provide a range header

GET /jaws HTTP/1.1
Host: localhost
Range: bytes=41000-49999

The response return just the requests bytes;

HTTP/1.1 206 Partial Content
Content-Type: video/mp4
Content-Range: bytes 41000-49999/60000
Content-Length: 9000
Accept-Ranges: bytes

[codecov]

Codecov Report

Attention: Patch coverage is 98.91304% with 1 line in your changes missing coverage. Please review.

Project coverage is 94.76%. Comparing base (e4e48d7) to head (14ba490).

Files with missing lines	Patch %	Lines
...lyingSocks/Sources/AsyncBufferedFileSequence.swift	97.05%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #157      +/-   ##
==========================================
+ Coverage   94.59%   94.76%   +0.16%     
==========================================
  Files          62       62              
  Lines        4032     4105      +73     
==========================================
+ Hits         3814     3890      +76     
+ Misses        218      215       -3     

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