Build modified streamline images

The official image from streamline does not currently work for the arm64
platform. As a temporary measure, the source code and docker build scripts
have been lifted from the official images and are used to build locally.

Some additional modifications are made to reduce overall image size, these
are documented in docker/README.md

docker/streamline-src/vendor/symfony/string/composer.json

@@ -0,0 +1,43 @@
+{
+    "name": "symfony/string",
+    "type": "library",
+    "description": "Provides an object-oriented API to strings and deals with bytes, UTF-8 code points and grapheme clusters in a unified way",
+    "keywords": ["string", "utf8", "utf-8", "grapheme", "i18n", "unicode"],
+    "homepage": "https://symfony.com",
+    "license": "MIT",
+    "authors": [
+        {
+            "name": "Nicolas Grekas",
+            "email": "p@tchwork.com"
+        },
+        {
+            "name": "Symfony Community",
+            "homepage": "https://symfony.com/contributors"
+        }
+    ],
+    "require": {
+        "php": ">=8.2",
+        "symfony/polyfill-ctype": "~1.8",
+        "symfony/polyfill-intl-grapheme": "~1.0",
+        "symfony/polyfill-intl-normalizer": "~1.0",
+        "symfony/polyfill-mbstring": "~1.0"
+    },
+    "require-dev": {
+        "symfony/error-handler": "^6.4|^7.0",
+        "symfony/intl": "^6.4|^7.0",
+        "symfony/http-client": "^6.4|^7.0",
+        "symfony/translation-contracts": "^2.5|^3.0",
+        "symfony/var-exporter": "^6.4|^7.0"
+    },
+    "conflict": {
+        "symfony/translation-contracts": "<2.5"
+    },
+    "autoload": {
+        "psr-4": { "Symfony\\Component\\String\\": "" },
+        "files": [ "Resources/functions.php" ],
+        "exclude-from-classmap": [
+            "/Tests/"
+        ]
+    },
+    "minimum-stability": "dev"
+}