[MRG] Proper links in release file in documentation

[rflamary]

Types of changes

The objective is to have links to Issues and PR when in the Release page in the docuemnation.

It is done with a simple sed before building the doc

Motivation and context / Related issue

How has this been tested (if it applies)

PR checklist

• I have read the CONTRIBUTING document.
• The documentation is up-to-date with the changes I made (check build artifacts).
• All tests passed, and additional code has been covered with new tests.
• I have added the PR and Issue fix to the RELEASES.md file.

[codecov]

Codecov Report

Merging #350 (0e580cb) into master (3302cd4) will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #350      +/-   ##
==========================================
+ Coverage   93.59%   93.63%   +0.03%     
==========================================
  Files          22       22              
  Lines        5591     5591              
==========================================
+ Hits         5233     5235       +2     
+ Misses        358      356       -2