Add support of another Fortran naming convention

[daloic]

By adding another scheme/language:

{ scheme: 'file', language: 'fortran_fixed-form' },

here:

https://github.com/hansec/vscode-fortran-ls/blob/15f08b0f1b667cb1da8a0010e5169d2e68ed53cd/src/extension.ts#L84

and adding the corresponding activation event in package.json:

"activationEvents": [
    "onLanguage:fortran",
    "onLanguage:fortran_fixed-form",
    "onLanguage:fortran-modern"
],

We can use the language server with modern Fortran extension.

Note that maybe it would be good if the authors of the Fortran extensions unite to have the same naming convention for fixed/modern Fortran id.