Add Plenti as a headless CMS option. (#857)

Author: jimafisk

src/site/headless-cms/plenti.md

@@ -0,0 +1,45 @@
+---
+title: Plenti
+repo: plentico/plenti
+homepage: https://plenti.co
+twitter: plentico
+opensource: "Yes"
+typeofcms: "Git-based"
+supportedgenerators:
+  - Plenti
+description: A git-backed, open-source editor that ships with your site, has live previews, minimal configuration, and zero vendor lock-in.
+---
+
+The Plenti CMS is designed to work out-of-the box with zero configuration. It's a "Discoverable CMS" that reads your content source and provides a default editing experience that you can use locally or deploy to a remote site and use CI. You can define defaults, schemas, and components to progressively enhance your editing experience if you so choose. Fundamentally:
+
+- Plenti saves content as JSON
+- Has no required keys / structure
+- Ships with your website to a CDN
+- Doesn't require any special hosting
+- Is built with Svelte
+- Doesn't require configuration
+- Can optionally define widget types
+- Supports component-based designs
+- Has live-previews
+- Uses OAuth (PKCE) from your git provider
+- Includes media management
+
+To see behind the scenes work on the CMS check out our [devlog series](https://www.youtube.com/watch?v=zPL8xrS9bVg&list=PLbWvcwWtuDm3vNn5ANzgVjyL1YOICT0jE).
+
+## Get Started
+
+To use Plenti, having Svelte experience is helpful, but good working knowledge of HTML/CSS fundamentals should be sufficient.
+
+You can download the [latest release](https://github.com/plentico/plenti/releases) from our repository (or use a package manager like snap or homebrew). 
+
+Then simply:
+1. Create a site: `plenti new site my-site` and `cd my-site`
+2. Start your local webserver: `plenti serve`
+3. Navigate to the test login page in your browser: http://localhost:3000/admin
+4. Click the "Login" button
+
+## Get Involved
+
+Want to help out with Plenti's development? You can [write code](https://github.com/plentico/plenti/pulls), [report a bug](https://github.com/plentico/plenti/issues), or [ask a question](https://github.com/plentico/plenti/discussions) on GitHub.
+
+We're completely self-funded and volunteer run, so if you'd like to support the project, please consider [making a donation](https://github.com/sponsors/plentico). Thank you!