patch 9.1.1935: filetype: not all Erlang files are recognized

Problem:  filetype: not all Erlang files are recognized
Solution: Detect *.app.src and rebar.config files as erlang filetype
          (John Parise).

*.app.src files contain Erlang application definitions. (There are also
*.app files, which are similar but more often build artifacts, and that
file extension is too ambiguous to be recognized by default.)

Reference:
- https://www.erlang.org/doc/system/applications.html

Rebar is the Erlang build tool. rebar.config uses Erlang syntax.

Reference:
- https://rebar3.org/docs/configuration/configuration/

closes: #18835

Signed-off-by: Jon Parise <jon@indelible.org>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/testdir/test_filetype.vim

@@ -275,7 +275,7 @@ def s:GetFilenameChecks(): dict<list<string>>
     elsa: ['file.lc'],
     elvish: ['file.elv'],
     epuppet: ['file.epp'],
-    erlang: ['file.erl', 'file.hrl', 'file.yaws'],
+    erlang: ['file.erl', 'file.hrl', 'file.yaws', 'file.app.src', 'rebar.config'],
     eruby: ['file.erb', 'file.rhtml'],
     esdl: ['file.esdl'],
     esmtprc: ['anyesmtprc', 'esmtprc', 'some-esmtprc'],

src/version.c

@@ -729,6 +729,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1935,
 /**/
     1934,
 /**/