blurbs.md: Allow blank lines before repo/branch

[damithc]

Current:

In the blurbs.md, the following works:

https://github.com/org1/repo1/tree/master

some info about repo1

<!--repo-->--------------------------------------------------------
https://github.com/org2/repo2/tree/master

some info about repo2

but the following does not (due to the blank line below the separator):

https://github.com/org1/repo1/tree/master

some info about repo1

<!--repo-->--------------------------------------------------------

https://github.com/org2/repo2/tree/master

some info about repo2

Suggestion: While not very important, we can also allow the 2nd one, simply by doing a trim()/strip() before processing each block of text.

Justification: the 2nd one is easier on the eye, when authoring the blurbs.md.