Add optional heapless v0.9

[diondokter]

No description provided.

[github-actions]

PR build size

  text	   data	    bss	    dec	    hex	filename
 16920	     56	  33808	  50784	   c660	example

Diff

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  +0.0%      +1  [ = ]       0    .debug_info
  +0.0%      +1  [ = ]       0    .strtab
  -0.0%      -1  [ = ]       0    .debug_str
  -1.6%      -1  [ = ]       0    [Unmapped]
  -0.0%      -8  [ = ]       0    .debug_line
  -0.0%      -8  [ = ]       0    TOTAL

[github-actions]

PR build size

  text	   data	    bss	    dec	    hex	filename
 16920	     56	  33808	  50784	   c660	example

Diff

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  +0.0%      +1  [ = ]       0    .debug_info
  +0.0%      +1  [ = ]       0    .strtab
  -0.0%      -1  [ = ]       0    .debug_str
  -1.6%      -1  [ = ]       0    [Unmapped]
  -0.0%      -8  [ = ]       0    .debug_line
  -0.0%      -8  [ = ]       0    TOTAL

[github-actions]

PR build size

  text	   data	    bss	    dec	    hex	filename
 16920	     56	  33808	  50784	   c660	example

Diff

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  +0.0%      +1  [ = ]       0    .debug_info
  +0.0%      +1  [ = ]       0    .strtab
  -0.0%      -1  [ = ]       0    .debug_str
  -1.6%      -1  [ = ]       0    [Unmapped]
  -0.0%      -8  [ = ]       0    .debug_line
  -0.0%      -8  [ = ]       0    TOTAL