Update docs, file formatting and docker images (#766)

* docs: fix wrong licence link

* fix: add more formatting settings, reformat all

feat: add vscode extensions recommendations

* docs: update contributing documentation

* fix: remove unnecessary comment

it was due to broken checkout

* docs: rework installation section

it has been brought up few times, new style should be easier
to understand

* docs: update images provided by catthehacker

* docs: replace 18.04 with recent image

* fix: add final new line

.vscode/extensions.json

@@ -0,0 +1,9 @@
+{
+  "recommendations": [
+    "editorconfig.editorconfig",
+    "golang.go",
+    "davidanson.vscode-markdownlint",
+    "esbenp.prettier-vscode",
+    "redhat.vscode-yaml"
+  ]
+}