gui: Translate fancytree messages in Versions modal (#8149)

* gui: Translate fancytree messages in Versions modal

Currently, the default fancytree info/error messages are used. This
means that a) they are English-only, and b) they are very generic. With
this commit, the messages are added to the translatable strings, and
they are also more specifically related to file versioning.

On a side note, the "moreData" string has been left out on purpose, as
it is not used in the current code. It can be added later if needed.

Signed-off-by: Tomasz Wilczyński <twilczynski@naver.com>

gui/default/assets/lang/lang-en.json

@@ -128,6 +128,7 @@
    "Error": "Error",
    "External File Versioning": "External File Versioning",
    "Failed Items": "Failed Items",
+   "Failed to load file versions.": "Failed to load file versions.",
    "Failed to load ignore patterns.": "Failed to load ignore patterns.",
    "Failed to setup, retrying": "Failed to setup, retrying",
    "Failure to connect to IPv6 servers is expected if there is no IPv6 connectivity.": "Failure to connect to IPv6 servers is expected if there is no IPv6 connectivity.",
@@ -373,6 +374,7 @@
    "The rate limit must be a non-negative number (0: no limit)": "The rate limit must be a non-negative number (0: no limit)",
    "The rescan interval must be a non-negative number of seconds.": "The rescan interval must be a non-negative number of seconds.",
    "There are no devices to share this folder with.": "There are no devices to share this folder with.",
+   "There are no file versions to restore.": "There are no file versions to restore.",
    "There are no folders to share with this device.": "There are no folders to share with this device.",
    "They are retried automatically and will be synced when the error is resolved.": "They are retried automatically and will be synced when the error is resolved.",
    "This Device": "This Device",