src/vs/workbench/services/mode/common/workbenchModeService.ts/WorkbenchModeServiceImpl/updateMime
class WorkbenchModeServiceImpl:	private updateMime(): void {
		const configuration = this._configurationService.getValue<IFilesConfiguration>();

		// Clear user configured mime associations
		mime.clearTextMimes(true /* user configured */);

		// Register based on settings
		if (configuration.files?.associations) {
			Object.keys(configuration.files.associations).forEach(pattern => {
				const langId = configuration.files.associations[pattern];
				const mimetype = this.getMimeForMode(langId) || `text/x-${langId}`;

				mime.registerTextMime({ id: langId, mime: mimetype, filepattern: pattern, userConfigured: true });
			});
		}

		this._onLanguagesMaybeChanged.fire();
	}