chore: readme updates

[ameypv-rudder]

Description

References our license file instead of redirecting the user to Elastic's site for licensing information.

Linear Ticket

< Replace with Linear Link >

Security

• The code changed/added as part of this pull request won't create any security issues with how the software is being used.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.02% ⚠️

Comparison is base (4abe28f) 69.11% compared to head (c7836d0) 69.10%.
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3822      +/-   ##
==========================================
- Coverage   69.11%   69.10%   -0.02%     
==========================================
  Files         349      349              
  Lines       51947    51947              
==========================================
- Hits        35905    35897       -8     
- Misses      13740    13744       +4     
- Partials     2302     2306       +4     

see 7 files with indirect coverage changes

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