Website update (#301)

* added two high-level paragraphs on model-based techniques

* Update jekyll/index.md: review suggestion TLA+ and Quint

Co-authored-by: Gabriela Moreira <gabrielamoreira05@gmail.com>

* switching MB Testing > MB Techniques, for a broader picture

---------

Co-authored-by: Gabriela Moreira <gabrielamoreira05@gmail.com>

jekyll/README.md

@@ -1,4 +1,4 @@
-# Jekyll Website for Model Based Testing
+# Jekyll Website for Model Based Techniques
 
 The website is live at [https://mbt.informal.systems](https://mbt.informal.systems)
 

jekyll/_config.yml

@@ -1,4 +1,4 @@
-title: Model Based Testing
+title: Model Based Techniques
 description: Part of Informal Systems
 baseurl: ""
 url: "https://mbt.informal.systems"

jekyll/docs/model.md

@@ -2,7 +2,7 @@
 title: Model extraction
 description: Extract abstract model from your implementation
 layout: default
-parent: Model Based Testing
+parent: Model Based Techniques
 nav_order: 2
 --- -->
 

jekyll/docs/modelator.md

@@ -2,7 +2,7 @@
 title: Modelator
 description: Tool to model based testing from Informal Systems
 layout: default
-parent: Model Based Testing
+parent: Model Based Techniques
 nav_order: 3
 ---
 

jekyll/index.md

@@ -1,14 +1,30 @@
 ---
 layout: default
-title: Model Based Testing
+title: Model Based Techniques
 nav_order: 1
-description: Model Based Testing in Informal Systems
+description: Model Based Techniques at Informal Systems
 has_children: true
 ---
 
-# Model Based Testing @ Informal Systems
+# Model Based Techniques for Software Correctness
+Building a model of our software gives us a couple of elegant and efficient ways to increase confidence in its correctness.
+Modeling languages (such as [TLA+](https://lamport.azurewebsites.net/tla/tla.html) and [Quint](https://github.com/informalsystems/quint)) are supported by _model checkers_, which enable us to reason about the model's properties.
+We can specify desired properties and verify that the model satisfies them. We can also generate a large number of tests directly from the model and run them against the implementation. 
 
-At Informal Systems we aim to incorporate formal methods into everyday development practice. On the practical side, we develop tools and techniques that help developers to increase confidence in their code via automated generation and execution of tests derived from TLA+ models. 
+A model can be written even before the development starts.
+This enables finding problems early on, in the development phase.
+
+Besides being a tool for finding difficult-to-spot problems, models serve as high-level, yet precise and executable specifications.
+
+
+# Model Based Techniques @ Informal Systems
+
+At Informal Systems, we use model-based techniques both in our development practice and as a part of our security audit services.
+We develop and maintain the following tools that make model-based techniques easy to incorporate in the development and auditing practice:
+ - [Quint](https://github.com/informalsystems/quint), a modern modeling language
+ - [Apalache](https://apalache.informal.systems/), a symbolic model checker
+ - [Modelator](https://github.com/informalsystems/modelator), a tool that enables automatic generation of tests from models
+ - [cosmwasm-to-quint](https://github.com/informalsystems/cosmwasm-to-quint), a tool for generating Quint model stubs and accompanying tests directly from [CosmWasm](https://cosmwasm.com/) contracts