Add @XSAM and @dmathieu as repository maintainers

[MrAlias]

After off-line discussions, the existing maintainers have all agreed that the contributions made by both @XSAM and @dmathieu motivate adding them as maintainers to the project. Both @XSAM and @dmathieu have confimed they are interested in the position and willing to accept the responsibilities.

TODO

• [ ] Add @XSAM to maintainers group
• [ ] Add @dmathieu to maintainers group
• [ ] Copy the substance of this PR into the contrib repository

[MrAlias]

@MadVikingGod as a codeowner, please take a look at this.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 84.4%. Comparing base (cff1a25) to head (965cf1b).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #5558     +/-   ##
=======================================
- Coverage   84.4%   84.4%   -0.1%     
=======================================
  Files        271     271             
  Lines      22333   22333             
=======================================
- Hits       18870   18868      -2     
- Misses      3132    3134      +2     
  Partials     331     331             

see 1 file with indirect coverage changes