Add page on What is Fontist?

.gitignore

@@ -9,5 +9,7 @@ _site/
 .jekyll-cache/
 .jekyll-metadata
 .DS_Store
+.bundle/
+Gemfile.lock
 
 .rubocop-https--*

_layouts/docs.html

@@ -0,0 +1,12 @@
+---
+layout: docs-base
+html-class: docs-page
+docs_title: Fontist
+navigation:
+  base_url: /docs
+  items:
+  - title: What is Fontist?
+    path: /
+---
+
+{{ content }}

_pages/docs.adoc

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+---
+layout: docs
+title: What is Fontist?
+html-class: overview
+---
+:page-liquid:
+
+= What is Fontist?
+
+Fontist is a simple library to find and download fonts for Windows, Linux and
+Mac.
+
+It uses a formula repository to find where to download a requested font. The
+main formula repository contains a lot of fonts, including Google Fonts, SIL
+Fonts, and macOS add-on fonts.
+
+== Why use Fontist when there are other ways to install fonts?
+
+In general, fonts can be downloaded manually and placed in a system folder.
+Some fonts are even pre-installed with an OS. But fontist allows to install
+fonts programmatically and consistently on all platforms (Windows, macOS, and
+Linux): missing fonts would be installed, existing ones would be found and
+their paths returned.
+
+=== Install font
+
+E.g., the following command would find where to download and install the Arial
+font:
+
+[source,sh]
+----
+fontist install "arial"
+----
+
+=== Install a bunch of fonts
+
+It also allows to install several fonts with a single command.
+
+Image you have a file:
+
+[source,yaml]
+----
+# manifest.yml
+---
+Times New Roman:
+Arial:
+Courier New:
+----
+
+Then running:
+
+[source,sh]
+----
+fontist manifest-install manifest.yml
+----
+
+Would install or find all 3 fonts, and return its paths.
+
+=== Use Ruby to install fonts
+
+Also Fontist allows to use its Ruby interface. The former tasks can be done with:
+
+[source,ruby]
+----
+Fontist::Font.install("arial")
+----
+
+[source,ruby]
+----
+Fontist::Manifest::Install.from_file("manifest.yml")
+----

nav-links.html

@@ -4,10 +4,14 @@
   <input type="search" id="siteSearchInput" placeholder="Type to search…">
 </div>
 
+{% include nav-page-link.html htmlclass="docs" url="/docs/" title="Docs" active_for_nested=true %}
+
 {% include nav-page-link.html htmlclass="software" url="/software/" title="Software" active_for_nested=true %}
 
 <!-- {% include nav-page-link.html htmlclass="fonts" url="/fonts/" title="Fonts" active_for_nested=true %} -->
 
 {% include project-nav.html %}
 
+{% include nav-page-link.html htmlclass="blog" url="/blog/" title="Blog" active_for_nested=true %}
+
 <a href="javascript: void 0;" class="search" aria-label="site search button"><i class="fas fa-search"></i></a>