Update PR-welcoming badge url

[jamesgeorge007]

Current Issue

Currently, the PR welcoming badge points to the repository itself which doesn't makes sense.

Proposed solution

Updated the link so that it points to creating a new PR.

[codecov]

Codecov Report

Merging #1299 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #1299   +/-   ##
======================================
  Coverage     100%    100%           
======================================
  Files           5       5           
  Lines         393     393           
======================================
  Hits          393     393

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