Tweak intro

Author: chenglou

pages/docs/manual/latest/introduction.mdx

@@ -18,7 +18,7 @@ We respect TypeScript very much and think that it's a positive force in the Java
 
 - Consequently, TypeScript's type system is necessarily complex, pitfalls-ridden, potentially requires tweaking, sometimes slow, and requires quite a bit of noisy annotations that often feel like manual bookkeeping rather than clear documentation. In contrast, ReScript's type system:
   - Is deliberately curated to be a simple subset most folks will have an easier time to use.
-  - Has **no** pitfalls, aka the type system is "sound" (the types will always be correct). E.g. If your value is not null, it'll never lie and slip through some `undefined` value. **ReScript code has no null errors**.
+  - Has **no** pitfalls, aka the type system is "sound" (the types will always be correct). E.g. If a type isn't marked as nullable, its value will never lie and let through some `undefined` value silently. **ReScript code has no null/undefined errors**.
   - Is the same for everyone. No knobs, no bikeshedding opportunity.
   - Runs extremely fast precisely thanks to its simplicity and curation. We're one of the fastest compiler & build system for JavaScript development.
   - **Doesn't need type annotations**. Annotate as much or as little as you'd like. The types are inferred by the language (and, again, are guaranteed correct).

pages/docs/manual/v8.0.0/introduction.mdx

@@ -8,7 +8,7 @@ canonical: "/docs/manual/latest/introduction"
 
 **ReScript is the language for folks who don't necessarily love JavaScript, but who still acknowledge its importance**.
 
-ReScript looks like JavaScript, works like JavaScript, works _with_ JavaScript, and compiles to the highest quality of clean, readable and performant JavaScript, directly runnable in the browser and Node.js. 
+ReScript looks like JavaScript, works like JavaScript, works _with_ JavaScript, and compiles to the highest quality of clean, readable and performant JavaScript, directly runnable in the browser and Node.js.
 
 ## Difference vs TypeScript
 
@@ -18,7 +18,7 @@ We respect TypeScript very much and think that it's a positive force in the Java
 
 - Consequently, TypeScript's type system is necessarily complex, pitfalls-ridden, potentially requires tweaking, sometime slow, and requires quite a bit of noisy annotations that often feel like manual bookkeeping rather than clear documentation. In contrast, ReScript's type system:
   - Is deliberately curated to be a simple subset most folks will have an easier time to use.
-  - Has **no** pitfalls, aka the type system is "sound" (the types will always be correct). E.g. If your value is not null, it'll never lie and slip through some `undefined` value. **ReScript code has no null errors**.
+  - Has **no** pitfalls, aka the type system is "sound" (the types will always be correct). E.g. If a type isn't marked as nullable, its value will never lie and let through some `undefined` value silently. **ReScript code has no null/undefined errors**.
   - Is the same for everyone. No knobs, no bikeshedding opportunity.
   - Runs extremely fast precisely thanks to its simplicity and curation. We're one of the fastest compiler & build system for JavaScript development.
   - **Doesn't need type annotations**. Annotate as much or as little as you'd like. The types are inferred by the language (and, again, are guaranteed correct).