Add `*.bbl-SAVE-ERROR` TeX.gitignore

[zhiyuanzhai]

This PR is proposing to add *.bbl-SAVE-ERROR to TeX.gitignore for BibLaTeX.

Reasons for making this change:

Recently I found that *.bbl-SAVE-ERROR files are generated in my LaTeX working directory, and I would like to exclude them from my git repository.

Links to documentation supporting these rule changes:

I do not recall when such files first appeared, but they appear in my working directory.

If this is a new template:

• Link to application or project’s homepage: Not a new template.

[wirecat]

@zhiyuanzhai would you be able to provide references to external documentation explaining what these files are? Otherwise I'm not comfortable pulling these changes in.