csl-lnum: submit corrections as pull requests

The csl-lnum repository was started to let users generate pull requests for dictionary-data corrections directly, lowering the barrier to contributing fixes.

Around the same time, the StarDict offline dictionaries gained correction-submission links and links to the scanned pages, so readers can cross-check an entry against the printed image and report errors. See the Contributing guide for the current correction workflow.

Sources: csl-lnum readme · csl-newsletter, October 2021.