Add acpi content for April 2021 (#55)

Author: IsaacWoods

content/this-month/2021-04/index.md

@@ -6,6 +6,7 @@ date = 0000-01-01
 month = "April 2021"
 authors = [
     "phil-opp",
+    "IsaacWoods",
     # add yourself here
 ]
 +++
@@ -78,7 +79,12 @@ This crate is still under depelopment. Some types or field accessors may be miss
 
 ### [`acpi`](https://github.com/rust-osdev/acpi)
 
-The `acpi` repository contains crates for parsing the ACPI tables – data structures that the firmware of modern computers use to relay information about the hardware to the OS. In April, ... TODO
+The `acpi` repository contains crates for parsing the ACPI tables – data structures that the firmware of modern computers use to relay information about the hardware to the OS.
+This month, we improved diagnostics by recording the original and target AML types in the `AmlError::IncompatibleValueConversion` error. This error is emitted when AML tries to convert a value
+to a data type that it can't be interpreted as - AML's rules on possible type conversions and where they can occur are very elaborate, so it helps to know the conversion that was actually attempted.
+<span class="gray">(published as `v0.12.0`)</span>
+
+Thanks to [@Knapsac](https://github.com/KnapSac) and [@toothbrush7777777](https://github.com/toothbrush7777777) for their contributions!
 
 ### [`uart_16550`](https://github.com/rust-osdev/uart_16550)