docs: Update CHANGELOG with v1.5.0 enhancements and features

Updated CHANGELOG to include details about the improvements and
new features introduced in version 1.5.0.

CHANGELOG.org

@@ -1,21 +1,26 @@
 #+TITLE: Changelog
 
 * v1.5.0    UNRELEASED
-- =Igist= now uses its own rendering engine instead of =tabulated-list-mode=. This improves performance.
-- Added new commands for filtering by languages, files, and description, which can be accessed with the transient prefix command - =igist-filters-menu=. By default, it is also bound to "/" in list buffers.
-- Added commands for adding and editing columns, which can be accessed with the transient prefix command - =igist-table-menu=. By default, it is also bound to "C" in list buffers.
-- Added a new command for cloning gists (=igist-clone-gist=). It is also bound to "C" in list buffers by default.
-- Added commands for forwarding entries and preview: =igist-list-backward-row-and-preview= (bound "C-M-n" in lists buffer) and =igist-list-backward-row-and-preview= (bound to "C-M-p" in lists buffer). 
-- New custom variables:
- + ~igist-user-gists-init-collapsed~: Whether the gists should be collapsed by default in user buffers.
- + ~igist-explore-gists-init-collapsed~: Whether the gists should be collapsed by default in explore buffers.
- + ~igist-clone-default-directory~: The default directory to use when =igist-clone-gist= reads the destination.
- + ~igist-use-header-line~: Whether the Igist List buffer should use a header line. If nil, an overlay will be used.
- + ~igist-tabulated-list-padding~: The number of characters preceding each Igist List mode entry.
- + ~igist-tabulated-list-tty-sort-indicator-desc~: Indicator for columns sorted in descending order, for =text-mode= frames.
- + ~igist-tabulated-list-tty-sort-indicator-asc~: Indicator for columns sorted in ascending order, for =text-mode= frames.
- + ~igist-tabulated-list-gui-sort-indicator-desc~: Indicator for columns sorted in descending order, for =gui= frames.
- + ~igist-tabulated-list-gui-sort-indicator-asc~: Indicator for columns sorted in ascending order, for =gui= frames.
+** Performance Improvements:
+ - The =igist= has switched to its own rendering engine from =tabulated-list-mode=, resulting in improved performance and more customization options. Additionally, a new mode for exploring public gists, called =igist-explore-mode=, has been derived from =igist-list-mode=.
+
+** Command changes:
+  - Improved the =igist-table-menu= function to increase its control over table columns. It now lets you dynamically modify several column properties, such as adding new columns, changing padding and alignment, renaming columns, modifying their width, and sorting them.
+  - Changed the behavior of =igist-tabulated-list-widen-current-column=. To avoid performance issues, some entries may now update to the new width immediately, while others may update after a slight delay. This debouncing mechanism prevents multiple quick successions of call executions, thereby improving overall performance and providing immediate visual feedback for the resizing operation.
+
+** New Commands:
+  - Added =igist-filters-menu=, a transient prefix command that allows for filtering by languages (=igist-toggle-language-filter=), files (=igist-search-files=), and descriptions (=igist-search-by-descriptions=). By default, it's bound to =/= in list buffers.
+  - Introduced =igist-clone-gist=, a new command for cloning gists, which is bound to =C= in list buffers by default.
+  - Introduced commands for navigating and previewing entries: =igist-list-backward-row-and-preview= (bound to =C-M-n= in lists buffer), and =igist-list-forward-row-and-preview= (bound to =C-M-p= in lists buffer).
+
+** Custom Variables:
+  - =igist-immediate-resize-strategy=: Controls the resizing strategy for tabulated entries when using =igist-tabulated-list-widen-current-column=.
+  - =igist-user-gists-init-collapsed= and =igist-explore-gists-init-collapsed=: Control the default collapsed state in user and exploration buffers, respectively.
+  - =igist-clone-default-directory=: Specifies the default directory for =igist-clone-gist=.
+  - =igist-use-header-line=: Determines whether the Igist List buffer uses a header line or an overlay.
+  - =igist-tabulated-list-padding=: Sets character padding for each Igist List mode entry.
+  - =igist-tabulated-list-tty-sort-indicator-desc=, =igist-tabulated-list-tty-sort-indicator-asc=: Indicate the sort order in =text-mode= frames.
+  - =igist-tabulated-list-gui-sort-indicator-desc=, =igist-tabulated-list-gui-sort-indicator-asc=: Indicate the sort order in =gui= frames.
 
 * v1.4.1    2023-08-19
 ** Fixes