Fix sponsor logos on dark mode and add past sponsors

.lycheeignore

@@ -15,3 +15,6 @@ dist/404/index.html$
 # Websites with aggressive rate limiting / bot detection
 https://www.nongnu.org/atool
 https://builtwith.com/
+
+# Open Collective returns 403 to automated checkers (bot detection)
+https://opencollective.com/

src/content/docs/internals/sponsors.md

@@ -9,20 +9,50 @@ We are looking for sponsors to make lychee's development sustainable.
 Please head over to our [Open Collective](https://opencollective.com/lychee-collective) or [book a meeting with the team](https://cal.com/lychee) if you want to support us as well.
 :::
 
-<h2 id="corrode">
-  <a href="https://corrode.dev">
-    <img src="/sponsors/corrode.svg" alt="Corrode logo" width="200" height="150" />
-  </a>
-</h2>
+<div class="sponsors">
+  <div class="sponsor">
+    <a class="sponsor-logo" href="https://corrode.dev">
+      <img src="/sponsors/corrode.svg" alt="corrode logo" width="200" />
+    </a>
+    <p class="sponsor-description">
+      corrode is a Rust consultancy that helps you build and maintain your Rust
+      services.
+    </p>
+  </div>
+  <div class="sponsor">
+    <a class="sponsor-logo" href="https://nlnet.nl/project/lychee/">
+      <img src="/sponsors/nlnet.svg" alt="NLnet logo" width="200" />
+    </a>
+    <p class="sponsor-description">
+      NLnet is supporting the open internet since 1997. lychee received financial
+      support through the <a href="https://nlnet.nl/core">NGI0 Core Fund</a>,
+      established by NLnet with financial support from the European Commission's
+      <a href="https://ngi.eu">Next Generation Internet</a> programme.
+    </p>
+  </div>
+</div>
 
-corrode is a Rust consultancy that helps you build and maintain your Rust
-services.
+## Past sponsors
 
-<h2 id="nlnet">
-  <a href="https://nlnet.nl/project/lychee/">
-    <img src="/sponsors/nlnet.svg" alt="NLnet logo" width="200" height="150" />
-  </a>
-</h2>
+A heartfelt thank you to those who supported lychee in the past.
 
-NLnet is supporting the open internet since 1997.
-lychee received financial support through the <a href="https://nlnet.nl/core">NGI0 Core Fund</a>, established by NLnet with financial support from the European Commission's <a href="https://ngi.eu">Next Generation Internet</a> programme.
+<div class="sponsors">
+  <div class="sponsor">
+    <a class="sponsor-logo" href="https://opencollective.com/suborbitaldev">
+      <img src="/sponsors/suborbital.svg" alt="Suborbital logo" width="200" />
+    </a>
+    <p class="sponsor-description">
+      Building the Suborbital Extension Engine (SE2) to make SaaS applications
+      extensible with user-provided plugins. Powered by WebAssembly.
+    </p>
+  </div>
+  <div class="sponsor">
+    <a class="sponsor-logo" href="https://determinate.systems/">
+      <img src="/sponsors/determinate.svg" alt="Determinate Systems logo" width="200" />
+    </a>
+    <p class="sponsor-description">
+      Determinate Systems brings Nix to the enterprise with secure, streamlined
+      tools that make software development and deployment reproducible everywhere.
+    </p>
+  </div>
+</div>

src/styles/index.css

@@ -112,6 +112,40 @@ h6 {
 	--sl-color-black: #17181c;
 }
 
+/* Sponsor cards. */
+.sponsors {
+	display: flex;
+	flex-direction: column;
+	gap: 1.5rem;
+	margin-top: 1.5rem;
+}
+
+.sponsor {
+	display: flex;
+	flex-wrap: wrap;
+	align-items: center;
+	gap: 1.25rem 1.75rem;
+}
+
+.sponsor-logo {
+	flex: 0 0 auto;
+	display: inline-flex;
+	/* White, padded background keeps dark logos readable in dark mode. */
+	background: #ffffff;
+	border-radius: 0.5rem;
+	padding: 1rem 1.25rem;
+}
+
+.sponsor-logo img {
+	width: 200px;
+	height: auto;
+}
+
+.sponsor-description {
+	flex: 1 1 16rem;
+	margin: 0;
+}
+
 /* Light mode colors. */
 :root[data-theme="light"] {
 	--sl-color-accent-low: #f0cbd9;