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/polyfill-intl-grapheme/README.md

@@ -0,0 +1,31 @@
+Symfony Polyfill / Intl: Grapheme
+=================================
+
+This component provides a partial, native PHP implementation of the
+[Grapheme functions](https://php.net/intl.grapheme) from the
+[Intl](https://php.net/intl) extension.
+
+- [`grapheme_extract`](https://php.net/grapheme_extract): Extract a sequence of grapheme
+  clusters from a text buffer, which must be encoded in UTF-8
+- [`grapheme_stripos`](https://php.net/grapheme_stripos): Find position (in grapheme units)
+  of first occurrence of a case-insensitive string
+- [`grapheme_stristr`](https://php.net/grapheme_stristr): Returns part of haystack string
+  from the first occurrence of case-insensitive needle to the end of haystack
+- [`grapheme_strlen`](https://php.net/grapheme_strlen): Get string length in grapheme units
+- [`grapheme_strpos`](https://php.net/grapheme_strpos): Find position (in grapheme units)
+  of first occurrence of a string
+- [`grapheme_strripos`](https://php.net/grapheme_strripos): Find position (in grapheme units)
+  of last occurrence of a case-insensitive string
+- [`grapheme_strrpos`](https://php.net/grapheme_strrpos): Find position (in grapheme units)
+  of last occurrence of a string
+- [`grapheme_strstr`](https://php.net/grapheme_strstr): Returns part of haystack string from
+  the first occurrence of needle to the end of haystack
+- [`grapheme_substr`](https://php.net/grapheme_substr): Return part of a string
+
+More information can be found in the
+[main Polyfill README](https://github.com/symfony/polyfill/blob/main/README.md).
+
+License
+=======
+
+This library is released under the [MIT license](LICENSE).