[libpng16] chore: Set the indent_size fields in .editorconfig

Also add an .editorconfig-checker.json file. We need to instruct the
editorconfig-checker program to skip the checks for the indent size.
(As of this commit time, editorconfig-checker is too rigid to recognize
"smart indentations".)

This is a cherry-pick of commit 67c99f75cf05b354f89c01c8fc15948300e84143
from branch 'libpng18'.

Co-authored-by: John Bowler <jbowler@acm.org>
Signed-off-by: John Bowler <jbowler@acm.org>
Signed-off-by: Cosmin Truta <ctruta@gmail.com>

.editorconfig

@@ -8,29 +8,41 @@ insert_final_newline = true
 trim_trailing_whitespace = true
 
 [*.txt]
+indent_size = unset
 indent_style = space
 
 [*.[chS]]
+indent_size = 3
 indent_style = space
 max_doc_length = 80
 max_line_length = 80
 
 [*.dfa]
+indent_size = 3
 indent_style = space
 max_doc_length = 80
 max_line_length = 80
 
-[*.{awk,cmake}]
+[*.awk]
+indent_size = 3
 indent_style = space
 max_doc_length = 80
 max_line_length = 100
 
-[*.{in,sh}]
+[*.cmake]
+indent_size = 2
+indent_style = space
+max_doc_length = 80
+max_line_length = 100
+
+[*.sh]
+indent_size = 4
 indent_style = space
 max_doc_length = 100
 max_line_length = 100
 
 [{Makefile.in,ltmain.sh}]
+indent_size = unset
 indent_style = unset
 insert_final_newline = unset
 max_doc_length = unset

.editorconfig-checker.json

@@ -0,0 +1,9 @@
+{
+  "Disable": {
+    "IndentSize": true
+  },
+  "Exclude": [
+    ".git/",
+    "out/"
+  ]
+}

contrib/.editorconfig

@@ -3,5 +3,7 @@
 root = false
 
 [*.[ch]]
+indent_size = unset
+indent_style = unset
 max_doc_length = unset
 max_line_length = unset

contrib/pngexif/.editorconfig

@@ -4,6 +4,7 @@ root = true
 
 [*]
 charset = utf-8
+indent_size = 4
 indent_style = space
 insert_final_newline = true
 max_doc_length = 79

contrib/visupng/.editorconfig

@@ -5,7 +5,8 @@ root = true
 [*]
 charset = utf-8
 end_of_line = unset
-indent_style = unset
+indent_size = 4
+indent_style = space
 insert_final_newline = true
 max_doc_length = 80
 max_line_length = 100