Install psalm as dev, sync scripts updates

vendor/felixfbecker/language-server-protocol/src/SignatureHelpClientCapabilities.php

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+<?php
+
+namespace LanguageServerProtocol;
+
+class SignatureHelpClientCapabilities
+{
+    /**
+     * Whether signature help supports dynamic registration.
+     *
+     * @var bool|null
+     */
+    public $dynamicRegistration;
+
+    /**
+     * The client supports the following `SignatureInformation`
+     * specific properties.
+     *
+     * @var SignatureHelpClientCapabilitiesSignatureInformation|null
+     */
+    public $signatureInformation;
+
+    /**
+     * The client supports to send additional context information for a
+     * `textDocument/signatureHelp` request. A client that opts into
+     * contextSupport will also support the `retriggerCharacters` on
+     * `SignatureHelpOptions`.
+     *
+     * @since 3.15.0
+     *
+     * @var bool|null
+     */
+    public $contextSupport;
+
+    public function __construct(
+        bool $dynamicRegistration = null,
+        SignatureHelpClientCapabilitiesSignatureInformation $signatureInformation = null,
+        bool $contextSupport = null
+    ) {
+        $this->dynamicRegistration = $dynamicRegistration;
+        $this->signatureInformation = $signatureInformation;
+        $this->contextSupport = $contextSupport;
+    }
+}