Fix some mistakes (#28)

Co-authored-by: Eldred Habert <eldredhabert0@gmail.com>

Author: lesleyrs

src/part1/header.md

@@ -145,10 +145,11 @@ So, we prevent disaster like this:
 {{#include ../assets/hello-world.asm:6:10}}
 ```
 
-The `ds` fills all bytes from $103 to $14F (inclusive) with the value $00.
+The directive `ds` stands for "define space", and allows filling a range of memory.
+This specific line fills all bytes from $103 to $14F (inclusive) with the value $00.
 Since different pieces of code and/or data cannot overlap, this ensures that the header's memory range can safely be overwritten by RGBFIX, and that nothing else accidentally gets steamrolled instead.
 
-It may not be obvious how the `ds` fills is told to fill this specific memory range.
+It may not be obvious how this `ds` ends up filling that specific memory range.
 The 3-byte `jp` covers memory addresses $100, $101, and $102.
 (We start at $100 because that's where the `SECTION` is hardcoded to be.)
 When RGBASM processes the `ds` directive, `@` (which is a special symbol that evaluates to "the current address") thus has the value $103, so it fills `$150 - $103 = $4D` bytes with zeros, so $103, $104, ..., $14E, $14F.

src/part1/jumps.md

@@ -9,7 +9,7 @@ Once this lesson is done, we will be able to understand all of `CopyTiles`!
 So far, all the code we have seen was linear: it executes top to bottom.
 But this doesn't scale: sometimes, we need to perform certain actions depending on the result of others ("if the crêpes start sticking, grease the pan again"), and sometimes, we need to perform actions repeatedly ("If there is some batter left, repeat from step 5").
 
-Both of these imply reading the recipe non-lineraly.
+Both of these imply reading the recipe non-linearly.
 In assembly, this is achieved using *jumps*.
 
 The CPU has a special-purpose register called "PC", for Program Counter.

src/part1/palettes.md

@@ -81,7 +81,7 @@ BGP immediately updates, turning the screen black!
 </figure>
 
 What if we wanted to take the original palette, but invert it?
-%11 would become %00, %01 would become %10, %10 would become %01, and %11 would become %00.
+%11 would become %00, %01 would become %10, %10 would become %01, and %00 would become %11.
 We would get thus:
 
 ```