Import SQLite-net source instead of built assembly

This should fix IL2CPP-enabled builds

Author: gilzoide

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "Plugins/sqlite-net~"]
+	path = Plugins/sqlite-net~
+	url = https://github.com/praeclarum/sqlite-net.git

Plugins/Makefile

@@ -31,6 +31,8 @@ BUILD_DIRS = \
 	build/webgl
 
 SQLITE_SRC = sqlite-amalgamation-3440200~/sqlite3.c
+SQLITE_NET_SRC = $(wildcard sqlite-net~/src/*.cs) sqlite-net~/LICENSE.txt
+SQLITE_NET_DEST = sqlite-net
 
 $(BUILD_DIRS):
 	mkdir -p $@
@@ -112,6 +114,9 @@ android-x86: build/android/x86/libsqlite3.so
 
 webgl: build/webgl/libsqlite3.bc
 
+source: $(SQLITE_NET_SRC)
+	cp $^ $(SQLITE_NET_DEST)
+
 all-android: android-arm64 android-arm32 android-x86_64 android-x86
 all-apple: macos-universal ios-universal tvos-universal visionos-universal
 all-linux: linux-x86_64