[doc] backport some readme improvements from v4

Author: gvergnaud

README.md

@@ -53,9 +53,9 @@ Write **better** and **safer conditions**. Pattern matching lets you express com
 
 ## What is Pattern Matching?
 
-Pattern Matching is a technique coming from functional programming languages to declaratively write conditional code branches based on the structure of a value. This technique has proven itself to be much more powerful and much less verbose than imperative alternatives (if/else/switch statements) especially when branching on complex data structures or on several values.
+Pattern Matching is a code-branching technique coming from functional programming languages, which let you scrutinize the structure of values in a declarative way. It has proven itself to be less verbose and more powerful than imperative alternatives (if/else/switch statements), especially when branching on complex data structures or on several values.
 
-Pattern Matching is implemented in Haskell, Rust, Swift, Elixir and many other languages. There is [a tc39 proposal](https://github.com/tc39/proposal-pattern-matching) to add Pattern Matching to the EcmaScript specification, but it is still in stage 1 and isn't likely to land before several years (if ever). Luckily, pattern matching can be implemented in userland. `ts-pattern` Provides a typesafe pattern matching implementation that you can start using today.
+Pattern Matching is implemented in Haskell, Rust, Swift, Elixir and many other languages. There is [a tc39 proposal](https://github.com/tc39/proposal-pattern-matching) to add Pattern Matching to the EcmaScript specification, but it is still in stage 1 and isn't likely to land before several years. Luckily, pattern matching can be implemented in userland. `ts-pattern` Provides a typesafe pattern matching implementation that you can start using today.
 
 Read the introduction blog post: [Bringing Pattern Matching to TypeScript 🎨 Introducing TS-Pattern v3.0](https://dev.to/gvergnaud/bringing-pattern-matching-to-typescript-introducing-ts-pattern-v3-0-o1k)
 
@@ -75,6 +75,8 @@ yarn add ts-pattern
 
 ### compatibility with different TypeScript versions
 
+Note: TS-Pattern assumes [Strict Mode](https://www.typescriptlang.org/tsconfig#strict) is enabled in your `tsconfig.json` file.
+
 | ts-pattern | TypeScript v4.2+ | TypeScript v4.1+ | TypeScript v3.x- |
 | ---------- | ---------------- | ---------------- | ---------------- |
 | v3.x       | ✅               | ⚠️               | ❌               |
@@ -95,6 +97,7 @@ yarn add ts-pattern
   - [`match`](#match)
   - [`.with`](#with)
   - [`.when`](#when)
+  - [`.exhaustive`](#exhaustive)
   - [`.otherwise`](#otherwise)
   - [`.run`](#run)
   - [`isMatching`](#ismatching)