Highlight zero-width space changes
### Summary
In GitLab's diffs, one cannot see that a line includes a [zero-width space change](https://en.wikipedia.org/wiki/Zero-width_space). As these spaces can break things, they should be highlighted.
### Steps to reproduce
Commit [a file with a zero-width space](https://gitlab.com/fdroid/repomaker/blob/a092f3d583cdecc8cd231dc352f633a814d43ae3/debian/data/org.fdroid.repomaker.appdata.xml) to a Git repo and push that repo to GitLab. Then, commit [an updated file without that zero-width space](https://gitlab.com/fdroid/repomaker/blob/9b1e98e257ff66a446f01d1a3ab487138830aaee/debian/data/org.fdroid.repomaker.appdata.xml) to Git and push the commit to GitLab. Take a look at the diff shown in GitLab.
### Example Project
See https://gitlab.com/fdroid/repomaker/merge_requests/206/diffs.
### What is the current *bug* behavior?
The diff shows a line change where it seems that nothing has changed.
### What is the expected *correct* behavior?
The zero-width space change is highlighted.
### Relevant logs and/or screenshots
`git diff` also doesn't highlight the change:
```diff
diff --git a/debian/data/org.fdroid.repomaker.appdata.xml b/debian/data/org.fdroid.repomaker.appdata.xml
index d5f5c05..198bb70 100644
--- a/debian/data/org.fdroid.repomaker.appdata.xml
+++ b/debian/data/org.fdroid.repomaker.appdata.xml
@@ -1,5 +1,5 @@
<?xml version="1.0" encoding="UTF-8"?>
-<component type="desktop-application">
+<component type="desktop-application">
<id>org.fdroid.repomaker</id>
<metadata_license>CC-BY-SA-4.0</metadata_license>
<project_license>AGPL-3.0</project_license>
```
`git commit -v` does highlight the change with `<200b>`:
```diff
diff --git a/debian/data/org.fdroid.repomaker.appdata.xml b/debian/data/org.fdroid.repomaker.appdata.xml
index d5f5c05..198bb70 100644
--- a/debian/data/org.fdroid.repomaker.appdata.xml
+++ b/debian/data/org.fdroid.repomaker.appdata.xml
@@ -1,5 +1,5 @@
<?xml version="1.0" encoding="UTF-8"?>
-<200b><component type="desktop-application">
+<component type="desktop-application">
<id>org.fdroid.repomaker</id>
<metadata_license>CC-BY-SA-4.0</metadata_license>
<project_license>AGPL-3.0</project_license>
```
### Output of checks
This bug happens on GitLab.com
issue