Document non-resource file handling in FileAccess and ResourceLoader

Author: Calinou

doc/classes/FileAccess.xml

@@ -34,7 +34,7 @@
 		[/codeblocks]
 		In the example above, the file will be saved in the user data folder as specified in the [url=$DOCS_URL/tutorials/io/data_paths.html]Data paths[/url] documentation.
 		[FileAccess] will close when it's freed, which happens when it goes out of scope or when it gets assigned with [code]null[/code]. [method close] can be used to close it before then explicitly. In C# the reference must be disposed manually, which can be done with the [code]using[/code] statement or by calling the [code]Dispose[/code] method directly.
-		[b]Note:[/b] To access project resources once exported, it is recommended to use [ResourceLoader] instead of [FileAccess], as some files are converted to engine-specific formats and their original source files might not be present in the exported PCK package.
+		[b]Note:[/b] To access project resources once exported, it is recommended to use [ResourceLoader] instead of [FileAccess], as some files are converted to engine-specific formats and their original source files might not be present in the exported PCK package. If using [FileAccess], make sure the file is included in the export by changing its import mode to [b]Keep File (exported as is)[/b] in the Import dock, or, for files where this option is not available, change the non-resource export filter in the Export dialog to include the file's extension (e.g. [code]*.txt[/code]).
 		[b]Note:[/b] Files are automatically closed only if the process exits "normally" (such as by clicking the window manager's close button or pressing [b]Alt + F4[/b]). If you stop the project execution by pressing [b]F8[/b] while the project is running, the file won't be closed as the game process will be killed. You can work around this by calling [method flush] at regular intervals.
 	</description>
 	<tutorials>

doc/classes/ResourceLoader.xml

@@ -7,6 +7,7 @@
 		A singleton used to load resource files from the filesystem.
 		It uses the many [ResourceFormatLoader] classes registered in the engine (either built-in or from a plugin) to load files into memory and convert them to a format that can be used by the engine.
 		[b]Note:[/b] You have to import the files into the engine first to load them using [method load]. If you want to load [Image]s at run-time, you may use [method Image.load]. If you want to import audio files, you can use the snippet described in [member AudioStreamMP3.data].
+		[b]Note:[/b] Non-resource files such as plain text files cannot be read using [ResourceLoader]. Use [FileAccess] for those files instead, and be aware that non-resource files are not exported by default (see notes in the [FileAccess] class description for instructions on exporting them).
 	</description>
 	<tutorials>
 		<link title="Operating System Testing Demo">https://godotengine.org/asset-library/asset/2789</link>