Move "themed" SVGs to imgs/src/

Those SVGs are not intended to be served stand-alone, so place them
in the directory that gets deleted in production (by the `pandocs` renderer).

src/Audio.md

@@ -6,7 +6,7 @@ Like much of its contemporary hardware, the Game Boy produces sound generated by
 
 ## Architecture
 
-{{#include imgs/apu_overview.svg:2:}}
+{{#include imgs/src/apu_overview.svg:2:}}
 
 The Game Boy has four sound generation units, called **channels** 1 through 4, notated "CH1", "CH2", etc.
 Unlike some other sound chips, such as the C64's SID or the Atari 5200's POKEY, each sound channel is specialized in a way largely different from the other channels.

src/Audio_details.md

@@ -42,7 +42,7 @@ tl;dr:
 </style>
 
 <figure>
-{{#include imgs/apu_detailed.svg:2:}}
+{{#include imgs/src/apu_detailed.svg:2:}}
 
 <figcaption>Source: Lior "LIJI32" Halphon</figcaption>
 </figure>
@@ -167,7 +167,7 @@ This only matters when changing the setting mid-playback: the digital values bei
 
 ### Noise channel (CH4)
 
-{{#include imgs/ch4_lfsr.svg:2:}}
+{{#include imgs/src/ch4_lfsr.svg:2:}}
 
 CH4 revolves around a [LFSR](https://en.wikipedia.org/wiki/Linear-feedback_shift_register), pictured above.
 The LFSR has 16 bits: 15 bits for its current state and 1 bit to temporarily store the next bit to shift in.

src/Rendering.md

@@ -25,7 +25,7 @@ During a frame, the Game Boy's PPU cycles between four modes as follows:
 
 </figcaption>
 
-{{#include imgs/ppu_modes_timing.svg:2:}}
+{{#include imgs/src/ppu_modes_timing.svg:2:}}
 
 </figure>
 

src/Tile_Data.md

@@ -86,7 +86,7 @@ example, the tile data `$3C $7E $42 $42 $42 $42 $42 $42 $7E $5E $7E $0A $7C $56
 $38 $7C` appears as follows:
 
 <figure>
-{{#include imgs/sprite.svg:2:}}
+{{#include imgs/src/sprite.svg:2:}}
 <figcaption>Sample tile data</figcaption>
 </figure>