fix(types): add some vim.fn type annotations

Problem: Some vim.fn have no type annotations.

Solution: Add type annotations.

runtime/lua/vim/_meta/vimfn.lua

@@ -2766,8 +2766,9 @@ function vim.fn.getchangelist(buf) end
 ---   endfunction
 --- <
 ---
+--- @param expr? 0|1
 --- @return integer
-function vim.fn.getchar() end
+function vim.fn.getchar(expr) end
 
 --- The result is a Number which is the state of the modifiers for
 --- the last obtained character with getchar() or in another way.
@@ -2837,8 +2838,9 @@ function vim.fn.getcharsearch() end
 --- Otherwise this works like |getchar()|, except that a number
 --- result is converted to a string.
 ---
+--- @param expr? 0|1
 --- @return string
-function vim.fn.getcharstr() end
+function vim.fn.getcharstr(expr) end
 
 --- Return the type of the current command-line completion.
 --- Only works when the command line is being edited, thus
@@ -5297,8 +5299,9 @@ function vim.fn.mapcheck(name, mode, abbr) end
 ---   ounmap xyzzy
 ---   echo printf("Operator-pending mode bit: 0x%x", op_bit)
 ---
---- @return any
-function vim.fn.maplist() end
+--- @param abbr? 0|1
+--- @return table[]
+function vim.fn.maplist(abbr) end
 
 --- Like |map()| but instead of replacing items in {expr1} a new
 --- List or Dictionary is created and returned.  {expr1} remains
@@ -7634,8 +7637,15 @@ function vim.fn.searchdecl(name, global, thisblock) end
 ---        \ 'synIDattr(synID(line("."), col("."), 0), "name") =~? "string"')
 --- <
 ---
---- @return any
-function vim.fn.searchpair() end
+--- @param start any
+--- @param middle any
+--- @param end_ any
+--- @param flags? string
+--- @param skip? any
+--- @param stopline? any
+--- @param timeout? integer
+--- @return integer
+function vim.fn.searchpair(start, middle, end_, flags, skip, stopline, timeout) end
 
 --- Same as |searchpair()|, but returns a |List| with the line and
 --- column position of the match. The first element of the |List|
@@ -7647,8 +7657,15 @@ function vim.fn.searchpair() end
 --- <
 --- See |match-parens| for a bigger and more useful example.
 ---
---- @return any
-function vim.fn.searchpairpos() end
+--- @param start any
+--- @param middle any
+--- @param end_ any
+--- @param flags? string
+--- @param skip? any
+--- @param stopline? any
+--- @param timeout? integer
+--- @return [integer, integer]
+function vim.fn.searchpairpos(start, middle, end_, flags, skip, stopline, timeout) end
 
 --- Same as |search()|, but returns a |List| with the line and
 --- column position of the match. The first element of the |List|

src/nvim/eval.lua

@@ -3448,7 +3448,7 @@ M.funcs = {
       <
     ]=],
     name = 'getchar',
-    params = {},
+    params = { { 'expr', '0|1' } },
     returns = 'integer',
     signature = 'getchar([{expr}])',
   },
@@ -3537,7 +3537,7 @@ M.funcs = {
       result is converted to a string.
     ]=],
     name = 'getcharstr',
-    params = {},
+    params = { { 'expr', '0|1' } },
     returns = 'string',
     signature = 'getcharstr([{expr}])',
   },
@@ -6482,7 +6482,8 @@ M.funcs = {
       	echo printf("Operator-pending mode bit: 0x%x", op_bit)
     ]],
     name = 'maplist',
-    params = {},
+    params = { { 'abbr', '0|1' } },
+    returns = 'table[]',
     signature = 'maplist([{abbr}])',
   },
   mapnew = {
@@ -9143,7 +9144,16 @@ M.funcs = {
       <
     ]=],
     name = 'searchpair',
-    params = {},
+    params = {
+      { 'start', 'any' },
+      { 'middle', 'any' },
+      { 'end', 'any' },
+      { 'flags', 'string' },
+      { 'skip', 'any' },
+      { 'stopline', 'any' },
+      { 'timeout', 'integer' },
+    },
+    returns = 'integer',
     signature = 'searchpair({start}, {middle}, {end} [, {flags} [, {skip} [, {stopline} [, {timeout}]]]])',
   },
   searchpairpos = {
@@ -9160,7 +9170,16 @@ M.funcs = {
       See |match-parens| for a bigger and more useful example.
     ]=],
     name = 'searchpairpos',
-    params = {},
+    params = {
+      { 'start', 'any' },
+      { 'middle', 'any' },
+      { 'end', 'any' },
+      { 'flags', 'string' },
+      { 'skip', 'any' },
+      { 'stopline', 'any' },
+      { 'timeout', 'integer' },
+    },
+    returns = '[integer, integer]',
     signature = 'searchpairpos({start}, {middle}, {end} [, {flags} [, {skip} [, {stopline} [, {timeout}]]]])',
   },
   searchpos = {