Create a /milestones endpoint which basically serves as a dashboard view for milestones, very similar to the /issues or /pulls page.

Closes #8232

* static url

* add cors support for static resources

* [assets] work on the migration to configurable url for assets

Signed-off-by: Jakob Ackermann <das7pad@outlook.com>

* [misc] fix whitespace

Signed-off-by: Jakob Ackermann <das7pad@outlook.com>

* [assets] fix the loading of the manifest.json

It is generated dynamically, and as such can not be served by the cdn.

Signed-off-by: Jakob Ackermann <das7pad@outlook.com>

* Revert "add cors support for static resources"

This reverts commit 42f964fd18

Signed-off-by: Jakob Ackermann <das7pad@outlook.com>

* [docs] add the STATIC_URL_PREFIX option

Signed-off-by: Jakob Ackermann <das7pad@outlook.com>

* [docs] reverse-proxy: nginx: add two setups for STATIC_URL_PREFIX

Signed-off-by: Jakob Ackermann <das7pad@outlook.com>

* [assets] migrate the url of a new asset to the static url prefix

REF: f2a3abc683
Signed-off-by: Jakob Ackermann <das7pad@outlook.com>

This change makes it easier to customize the header and footer content. Before this change, the whole header and footer had to be overridden, including the meta, style and script tags.

Signed-off-by: Lukas Bestle <mail@lukasbestle.com>