feat: add filename_small_case (#344)

Add an option to cast the new filename to lowercase. Closes #311.

doc/telekasten.txt

@@ -309,6 +309,19 @@ telekasten.setup({opts})
 
         Default: `nil`
 
+                                 *telekasten.settings.filename_small_case*
+    filename_small_case: ~
+        When the note title is used within the filename, i.e.
+        |new_note_filename| contains 'title', the tile will be 
+        made lowercase.
+
+        e.g. if set to true, '20230103-My New Note Title.md' would instead
+        become '20230103-my new note title.md'
+
+        If set to `false`, no substitution will occur.
+
+        Default: `false`
+
                                     *telekasten.settings.image_link_style*
     image_link_style: ~
         Style of links to insert when pasting an image.

lua/telekasten.lua

@@ -73,6 +73,8 @@ local function defaultConfig(home)
         uuid_sep = "-",
         -- if not nil, replaces any spaces in the title when it is used in filename generation
         filename_space_subst = nil,
+        -- if true, make the filename lowercase
+        filename_small_case = false,
         -- following a link to a non-existing note will create it
         follow_creates_nonexisting = true,
         dailies_create_nonexisting = true,
@@ -180,6 +182,10 @@ local function generate_note_filename(uuid, title)
         title = title:gsub(" ", M.Cfg.filename_space_subst)
     end
 
+    if M.cfg.filename_small_case then
+        title = string.lower(title)
+    end
+
     local pp = Path:new(title)
     local p_splits = pp:_split()
     local filename = p_splits[#p_splits]