Make rmarkdown files work with styler and lintr (#2564)

* add R markdown as filetype for styler
* Add rmarkdown as an alias for R

autoload/ale/fix/registry.vim

@@ -297,7 +297,7 @@ let s:default_registry = {
 \   },
 \   'styler': {
 \       'function': 'ale#fixers#styler#Fix',
-\       'suggested_filetypes': ['r'],
+\       'suggested_filetypes': ['r', 'rmarkdown'],
 \       'description': 'Fix R files with styler.',
 \   },
 \   'latexindent': {

autoload/ale/linter.vim

@@ -13,6 +13,7 @@ let s:default_ale_linter_aliases = {
 \   'Dockerfile': 'dockerfile',
 \   'csh': 'sh',
 \   'plaintex': 'tex',
+\   'rmarkdown': 'r',
 \   'systemverilog': 'verilog',
 \   'verilog_systemverilog': ['verilog_systemverilog', 'verilog'],
 \   'vimwiki': 'markdown',

doc/ale.txt

@@ -1012,6 +1012,7 @@ g:ale_linter_aliases                                     *g:ale_linter_aliases*
   \   'Dockerfile': 'dockerfile',
   \   'csh': 'sh',
   \   'plaintex': 'tex',
+  \   'rmarkdown': 'r',
   \   'systemverilog': 'verilog',
   \   'verilog_systemverilog': ['verilog_systemverilog', 'verilog'],
   \   'vimwiki': 'markdown',