Add OpenWRT Makefile

[kmiracle86]

• Tested on MIPS (Gl.Inet Mudi E750) with rtsp

[codecov-commenter]

Codecov Report

Merging #970 (25be676) into main (ea158ca) will decrease coverage by 0.01%. The diff coverage is n/a.

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@@            Coverage Diff             @@
##             main     #970      +/-   ##
==========================================
- Coverage   65.66%   65.65%   -0.01%     
==========================================
  Files         118      118              
  Lines       12906    12906              
==========================================
- Hits         8475     8474       -1     
- Misses       3761     3762       +1     
  Partials      670      670              

Impacted Files	Coverage Δ
internal/core/source_static.go	67.39% <0.00%> (-2.90%)	:arrow_down:
internal/core/rtsp_source.go	50.90% <0.00%> (-1.22%)	:arrow_down:
internal/core/hls_server.go	76.63% <0.00%> (-0.41%)	:arrow_down:
internal/core/path.go	73.55% <0.00%> (-0.34%)	:arrow_down:
internal/hls/client_processor_fmp4.go	64.88% <0.00%> (ø)
internal/core/webrtc_conn.go	55.38% <0.00%> (+0.66%)	:arrow_up:
internal/core/rtmp_source.go	67.80% <0.00%> (+2.73%)	:arrow_up:

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[aler9]

The provided Makefile has been adapted in order to

• fix compatibility with latest OpenWRT
• be independent from a specific version
• provide server version to the server executable

The README has been updated with instructions that describes how to use this Makefile to install for OpenWRT.