Add nlnet and prototype fund logos

This change adds entities that currently support diesel's development
with significant sponsorships/funds as notable sponsors on the web page.
For ProtoType fund and the Federal Ministry of Research that's a
requirement for their funding. For the other entities it's just fair to
have them there as well as they contribute similar amount of funding.

Author: weiznich

README.md

@@ -263,3 +263,50 @@ for useful information about setting up Diesel locally, coding style and common
 Unless you explicitly state otherwise, any contribution you intentionally submit
 for inclusion in the work, as defined in the Apache-2.0 license, shall be
 dual-licensed as above, without any additional terms or conditions.
+
+### Notable Sponsors and Supporters
+
+We would like to thank all of the sponsors supporting the work on Diesel. Notable large sponsors are:
+
+
+<p align="center">
+    <a href="https://nlnet.nl/project/Diesel/">
+        <img src="https://diesel.rs/assets/images/nl_net_foundation_logo.svg" width="50%"/>
+        <br/>
+        NLNet Foundation
+    </a>
+</p>
+
+<p align="center">
+    <a href="https://nlnet.nl/project/Diesel/">
+        <img src="https://diesel.rs/assets/images/NGI0Core_tag.svg" width="50%"/>
+        <br/>
+        NGI Zero Core
+    </a>
+</p>
+
+<p align="center">
+    <a href="https://www.prototypefund.de/projects/diesel-databaseviews">
+        <img src="https://diesel.rs/assets/images/PrototypeFund_logo_dark.png" width="50%"/>
+        <br/>
+        Prototype Fund
+    </a>
+</p>
+
+<p align="center">
+    <a href="https://www.prototypefund.de/projects/diesel-databaseviews">
+        <img src="https://diesel.rs/assets/images/bmbf_logo.jpg" width="50%"/>
+        <br/>
+        Federal Ministry of Research, Technology and Space (Germany)
+    </a>
+</p>
+
+<p align="center">
+    <a href="https://giga-infosystems.com/">
+        <img src="https://diesel.rs/assets/images/logo_giga.svg" width="35%"/>
+        <br/>
+        GiGa Infosystems GmbH
+    </a>
+</p>
+
+Additionally we would like to thank all persons sponsoring the project on [GitHub](https://github.com/sponsors/weiznich#sponsors). Without them developing Diesel wouldn't be possible.