Slash Inserter: Multi-character search of block name with Umlaut fails

[brentswisher]

Describe the bug
When attempting to insert a heading in german (Überschrift).
Using the slash inserter, "/U" shows Überschrift, but "/Ub" shows nothing.
Using the other keywords for "Überschrift" - Either "Untertitel" or "Titel" work as you type the entire word.

To Reproduce
Steps to reproduce the behavior:

1. Open new post in site set to the German language
2. Using slash inserter, type /Ub
3. See that the Überschrift option diappears.

Expected behavior
To be able to type any amount of the letters in "Überschrift" and have it still show as an option

Screenshots

Desktop (please complete the following information):

• OS: macOS 10.13.6
• Browser Chrome
• Version 69.0.3497.100

Additional context
Gutenberg Version 4.0.0

I discovered this while testing #10770 as a fix for #10489. However, this bug appears in master when using /U, and also in my branch using either U or Ü.
I don't believe that my changes had any effect on this bug, but it may be a related issue.

[Soean]

If you type /U you see Überschrift because of the Keyword Untertitel.
If you type /Ub you don't see a block because it's different from the block name and keywords.

[brentswisher]

I see that you are saying, but I think there may still be an issue. In the search in the upper left corner, if I enter /Uber, Überschrift will show up, but not in the autocomplete. I would expect them to be the same. Following that thought process, both /U and /Ub should trigger Überschrift - even though they are different letters.

Also, in #10770, where I have fixed it so that /Ü will show Überschrift, if I type /Üb it disappears, which maybe illustrates the issue a little clearer.

Let me know if that makes sense, I only speak a very small amount of German (still learning!) so I'm trying to follow the conventions that were already there in gutenberg for how to handle Umlauts, feel free to correct me if I am approaching this wrong.

[Soean]

I think your PR adds deburr just to the search term not to the bock name and keywords.
So with /Ü --> /U You match Untertitel and not Überschrift. This is why /Übdoesn't work.

[brentswisher]

Closing as duplicate, this is the same as issue #10489 which I have addressed in #10770, I just didn't realize it.