Feature/mkdocs with versioning (#333)

* docs: restructuring & introduction of mkdocs with versioning provided by mike

* docs: ad repositories section to sophia examples

* docs: refactoring and consistent naming of æternity

* docs: hint for new file destination

* docs: revert capital letter

* docs: accept proposed changes

* docs: fix anchors in stdlib

.docssite/mkdocs.yml

@@ -0,0 +1,55 @@
+site_name: æternity Sophia Language
+plugins:
+  - search
+  - mkdocs-simple-hooks:
+      hooks:
+        on_pre_build: 'hook:pre_build'
+repo_url: 'https://github.com/aeternity/aesophia'
+edit_uri: ''
+
+extra:
+  version:
+    provider: mike
+
+theme:
+  favicon: favicon.png
+  name: material
+  custom_dir: overrides
+  language: en
+  palette:
+    - scheme: default
+      primary: pink
+      accent: pink
+      toggle:
+        icon: material/weather-night
+        name: Switch to dark mode
+    - scheme: slate
+      primary: pink
+      accent: pink
+      toggle:
+        icon: material/weather-sunny
+        name: Switch to light mode
+  features:
+    - content.tabs.link
+    - search.highlight
+    - search.share
+    - search.suggest
+
+  # Don't include MkDocs' JavaScript
+  include_search_page: false
+  search_index_only: true
+
+markdown_extensions:
+  - admonition
+  - pymdownx.highlight
+  - pymdownx.superfences
+  - toc:
+      toc_depth: 3
+
+nav:
+  - Introduction: index.md
+  - Syntax: sophia_syntax.md
+  - Features: sophia_features.md
+  - Standard library: sophia_stdlib.md
+  - Contract examples: sophia_examples.md
+  - Changelog: CHANGELOG.md