Add quality check and cleanup for problematic unicode characters

[tobiasdiez]

Is your suggestion for improvement related to a problem? Please describe.

Some unicode characters make problems, even with biblatex support (eg pdflatex still not completely supporting unicode). For example, Garcı́a gives

Package inputenc Error: Unicode character ́ (U+0301)

A few of such problematic characters are:

• U+0300: https://tex.stackexchange.com/questions/555086/package-inputenc-error-unicode-char-%cc%80-u300-inputenc-not-set-up-for-use-wit
• U+0301: see https://tex.stackexchange.com/questions/329239/how-to-solve-a-unicode-char-u301-error and https://tex.stackexchange.com/questions/443018/package-inputenc-error-unicode-char-%cc%81-u301inputenc?noredirect=1&lq=1
• U+2212: https://tex.stackexchange.com/questions/361019/unicode-error-in-inputenc-package

Describe the solution you'd like

As these characters are hard to recognize, it would be nice if there would be an integrity check warning about them, and an automatic cleanup to convert them to their unproblematic equivalents (e.g. 0131 + 0301 to 00ED).

Additional context
Might be helpful: https://github.com/zepinglee/citeproc-lua/blob/ab3ce712cc92073f12be26ff0b22b30eb906092d/citeproc/citeproc-latex-data.lua#L517

[Siedlerchr]

Have you tried converting them to latex? We have latex2unicode and vice versa conversion already

[tobiasdiez]

It actually came from latex code that I converted to unicode (I want all my stuff in unicode). This is also not very helpful in recognizing which entry/field has the problematic character.