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

		// Clear user configured mime associations
		clearConfiguredLanguageAssociations();

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

				registerConfiguredLanguageAssociation({ id: langId, mime: mimeType, filepattern: pattern });
			});
		}

		this._onDidChange.fire();
	}