Add note to INSTALL.md about Chez thread support requirement when
Add note to INSTALL.md about Chez thread support requirement when

building Chez Scheme locally from source and
improve formatting of first paragraphs

```
Compiling idris2_app/idris2-boot.ss with output to
idris2_app/idris2-boot.so
Exception: attempt to reference unbound identifier
make-thread-parameter at line 171, char 30 of idris2_app/idris2-boot.ss
```

mmhelloworld/idris-jvm,mmhelloworld/idris-jvm,mmhelloworld/idris-jvm,mmhelloworld/idris-jvm,mmhelloworld/idris-jvm,mmhelloworld/idris-jvm