fix(treesitter): Add indentation fallback

[sebastianstudniczek]

Add fallback for languages which does not have indent query available, therefore neovim will use the built in indentation functions.

For example C# currently does not have treesitter indent query available

Installed languages     H L F I J ~
- bash                  ✓ ✓ ✓ ✓ ✓
- c                     ✓ ✓ ✓ ✓ ✓
- c_sharp               ✓ ✓ ✓ . ✓
- diff                  ✓ . ✓ . ✓
- dtd                   ✓ ✓ ✓ . ✓

Output from checking indentexpr for C# file after change

20:13:49 msg_show.list_cmd   set indentexpr?   indentexpr=GetCSIndent(v:lnum)