I believe this change allows for having multiple 'by' rules in the same
category. It seems to be working well for my purposes, but I would
appreciate further testing to assure there aren't regressions.

Example:

#template 300 by 2023-06
#template 3000 by 2023-08

Before this PR, having these two lines in the notes would only budget
funds for the earliest of the two strings and ignore the 3000 funding
target. With this PR, the sum of the two funding targets will be
respected.