Add multiple descriptions to several classes

This pull request adds several descriptions to multiple different classes.

This improves the completeness of the documentation and enhances usability by doing so.

doc/classes/EditorPlugin.xml

@@ -547,6 +547,7 @@
 			<return type="void">
 			</return>
 			<description>
+				Minimizes the bottom panel.
 			</description>
 		</method>
 		<method name="make_bottom_panel_item_visible">
@@ -555,6 +556,7 @@
 			<argument index="0" name="item" type="Control">
 			</argument>
 			<description>
+				Makes a specific item in the bottom panel visible.
 			</description>
 		</method>
 		<method name="queue_save_layout">

doc/classes/LineEdit.xml

@@ -169,6 +169,7 @@
 			The caret's column position inside the [LineEdit]. When set, the text may scroll to accommodate it.
 		</member>
 		<member name="caret_force_displayed" type="bool" setter="set_caret_force_displayed" getter="is_caret_force_displayed" default="false">
+			If [code]true[/code], the [LineEdit] will always show the caret, even if focus is lost.
 		</member>
 		<member name="caret_mid_grapheme" type="bool" setter="set_caret_mid_grapheme_enabled" getter="is_caret_mid_grapheme_enabled" default="false">
 			Allow moving caret, selecting and removing the individual composite character components.

doc/classes/Popup.xml

@@ -13,6 +13,7 @@
 	<members>
 		<member name="borderless" type="bool" setter="set_flag" getter="get_flag" override="true" default="true" />
 		<member name="close_on_parent_focus" type="bool" setter="set_close_on_parent_focus" getter="get_close_on_parent_focus" default="true">
+			If [code]true[/code], the [Popup] will close when its parent is focused.
 		</member>
 		<member name="transient" type="bool" setter="set_transient" getter="is_transient" override="true" default="true" />
 		<member name="unresizable" type="bool" setter="set_flag" getter="get_flag" override="true" default="true" />

doc/classes/TextEdit.xml

@@ -14,6 +14,7 @@
 			<return type="void">
 			</return>
 			<description>
+				A virtual method that is called whenever backspace is triggered.
 			</description>
 		</method>
 		<method name="add_gutter">
@@ -28,6 +29,7 @@
 			<return type="void">
 			</return>
 			<description>
+				Causes the [TextEdit] to perform a backspace.
 			</description>
 		</method>
 		<method name="center_viewport_to_cursor">
@@ -172,6 +174,7 @@
 			<argument index="0" name="line" type="int">
 			</argument>
 			<description>
+				Returns the indent level of a specific line.
 			</description>
 		</method>
 		<method name="get_line" qualifiers="const">
@@ -312,6 +315,7 @@
 			<return type="int">
 			</return>
 			<description>
+				Returns the [TextEdit]'s' tab size.
 			</description>
 		</method>
 		<method name="get_visible_line_count" qualifiers="const">
@@ -667,6 +671,7 @@
 			<argument index="0" name="size" type="int">
 			</argument>
 			<description>
+				Sets the tab size for the [TextEdit] to use.
 			</description>
 		</method>
 		<method name="undo">

doc/classes/Tree.xml

@@ -294,6 +294,7 @@
 			<argument index="0" name="item" type="Object">
 			</argument>
 			<description>
+				Causes the [Tree] to jump to the specified item.
 			</description>
 		</method>
 		<method name="set_column_clip_content">