fix(ts): Publish downleveled TS3.8 types, fix types path (#8954)

Author: krystofwoldrich

.npmignore

@@ -6,3 +6,4 @@
 !/cjs/**/*
 !/esm/**/*
 !/types/**/*
+!/types-ts3.8/**/*

packages/gatsby/.npmignore

@@ -6,6 +6,7 @@
 !/cjs/**/*
 !/esm/**/*
 !/types/**/*
+!/types-ts3.8/**/*
 
 # Gatsby specific
 !gatsby-browser.js

scripts/prepack.ts

@@ -23,6 +23,12 @@ const buildDir = packageWithBundles ? NPM_BUILD_DIR : BUILD_DIR;
 
 type PackageJsonEntryPoints = Record<typeof ENTRY_POINTS[number], string>;
 
+interface TypeVersions {
+  [key: string]: {
+    [key: string]: string[];
+  };
+};
+
 interface PackageJson extends Record<string, unknown>, PackageJsonEntryPoints {
   [EXPORT_MAP_ENTRY_POINT]: {
     [key: string]: {
@@ -31,11 +37,7 @@ interface PackageJson extends Record<string, unknown>, PackageJsonEntryPoints {
       types: string;
     };
   };
-  [TYPES_VERSIONS_ENTRY_POINT]: {
-    [key: string]: {
-      [key: string]: string[];
-    };
-  };
+  [TYPES_VERSIONS_ENTRY_POINT]: TypeVersions;
 }
 
 // eslint-disable-next-line @typescript-eslint/no-var-requires
@@ -81,7 +83,8 @@ if (newPkgJson[EXPORT_MAP_ENTRY_POINT]) {
 if (newPkgJson[TYPES_VERSIONS_ENTRY_POINT]) {
   Object.entries(newPkgJson[TYPES_VERSIONS_ENTRY_POINT]).forEach(([key, val]) => {
     newPkgJson[TYPES_VERSIONS_ENTRY_POINT][key] = Object.entries(val).reduce((acc, [key, val]) => {
-      return { ...acc, [key]: val.map(v => v.replace(`${buildDir}/`, '')) };
+      const newKey = key.replace(`${buildDir}/`, '');
+      return { ...acc, [newKey]: val.map(v => v.replace(`${buildDir}/`, '')) };
     }, {});
   });
 }