doc: documentation is now in the same repository as the code

Demo site will be generated in subfolder /demo

docs/config/sidebar.md

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+# Sidebar
+
+Settings related with left-side sidebar.
+
+Fields are under `[Params.Sidebar]` section.
+
+## compact
+
+- Type: `bool`
+- Default: `false`
+
+Enable compact version of sidebar.
+
+## emoji
+
+- Type: `string`
+
+Emoji displayed above the avatar.
+
+## subtitle
+
+- Type: `string`
+
+Subtitle displayed below the site title.
+
+## avatar
+
+- Type: `map[string]:(bool|string)`
+
+Configurations related with avatar.
+
+### avatar.enable
+
+- Type: `bool`
+- Default: `true`
+
+Enable avatar.
+
+### avatar.src
+
+- Type: `string`
+- Default: `img/avatar.png`
+
+Path to avatar image.
+
+### avatar.local
+
+- Type: `bool`
+- Default: `true`
+
+If `true`, the avatar image should be placed at `assets/${avatar.src}`, this allows theme to automatically resize the image.