Add Backstage logo assets (#2395)

* Add Backstage logo assets

* Update logos.md

* Update logos.md

* docs/verify-links: allow absolute URLs into microsite/static

Co-authored-by: Patrik Oldsberg <poldsberg@gmail.com>

docs/overview/logos.md

@@ -0,0 +1,41 @@
+---
+id: logos
+title: Logos
+sidebar_label: Logo assets
+---
+
+Guidelines for how to use the Backstage logo and icon can be found
+[here](/logo_assets/Backstage_Identity_Assets_Overview.pdf). The assets below
+are all in `.svg` format. Other formats are available in the
+[repository](https://github.com/spotify/backstage/tree/master/microsite/static/logo_assets).
+
+## Backstage logo
+
+<a href="/logo_assets/svg/Logo_White.svg">
+  <img src="/logo_assets/svg/Logo_White.svg" width="600" />
+</a>
+
+<a href="/logo_assets/svg/Logo_Teal.svg">
+  <img src="/logo_assets/svg/Logo_Teal.svg" width="600" />
+</a>
+
+<a href="/logo_assets/svg/Logo_Black.svg">
+  <img src="/logo_assets/svg/Logo_Black.svg" width="600" style="background-color:white" />
+</a>
+
+## Backstage icon
+
+<div>
+  <a href="/logo_assets/svg/Icon_White.svg">
+    <img src="/logo_assets/svg/Icon_White.svg" width="180" height="180" />
+  </a>
+  <a href="/logo_assets/svg/Icon_Teal.svg">
+    <img src="/logo_assets/svg/Icon_Teal.svg" width="180" height="180" />
+  </a>
+  <a href="/logo_assets/svg/Icon_Gradient.svg">
+    <img src="/logo_assets/svg/Icon_Gradient.svg" width="180" height="180" />
+  </a>
+  <a href="/logo_assets/svg/Icon_Black.svg">
+    <img src="/logo_assets/svg/Icon_Black.svg" width="180" height="180" style="background-color:white" />
+  </a>
+</div>

docs/verify-links.js

@@ -53,6 +53,11 @@ async function verifyUrl(basePath, url) {
       return { url, basePath, problem: 'not-relative' };
     }
 
+    const staticPath = resolvePath(projectRoot, 'microsite/static', `.${url}`);
+    if (await fs.pathExists(staticPath)) {
+      return;
+    }
+
     path = resolvePath(projectRoot, `.${url}`);
   } else {
     path = resolvePath(dirname(resolvePath(projectRoot, basePath)), url);
@@ -103,7 +108,9 @@ async function main() {
     console.log(`Found ${badUrls.length} bad links within repo`);
     for (const { url, basePath, problem } of badUrls) {
       if (problem === 'missing') {
-        console.error(`Unable to reach ${url}, linked from ${basePath}`);
+        console.error(
+          `Unable to reach ${url} from root or microsite/static/, linked from ${basePath}`,
+        );
       } else if (problem === 'not-relative') {
         console.error('Links to /docs/ must be relative');
         console.error(`  From: ${basePath}`);