Problem for adding plugin to TinyMCE

[benhaynes]

From directus created by dario30186 : directus/directus#2214

Hello,
I'm using directus v6.4.9
I'm trying to add the plugin textcolor to TinyMCE. If I modifiy the file app/core/interfaces/wysiwyg_full/interface.js and I add the plugin in options object and then I run again composer install it does not work. Even if I add "forecolor backcolor" to the interface options for WYSIWYG it doesn't work.
What can I do say to directus to take into account the textcolor plugin ?
Is it normal that when I modify the file app/core/interfaces/wysiwyg_full/interface.js and then I run again the command:
composer install

the output is:
Loading composer repositories with package information
Installing dependencies (including require-dev) from lock file
Nothing to install or update
Generating autoload files

So my modification is not loaded I think

Thank you in advance