Add TypeScript support.

Add TypeScript support.

* autopull.sh: Check out tree-sitter-typescript. Set
TREE_SITTER_TYPESCRIPT_VERSION.
* gettext-tools/build-aux/tree-sitter-typescript-portability.diff: New file.
* gettext-tools/configure.ac: Set TREE_SITTER_TYPESCRIPT_VERSION.
* gettext-tools/Makefile.am (EXTRA_DIST): Add the tree-sitter-typescript source
code and patch.
* gettext-tools/doc/lang-typescript.texi: New file.
* gettext-tools/doc/Makefile.am (gettext_TEXINFOS): Add it.
* gettext-tools/doc/gettext.texi (No string concatenation): Mention string
concatenation in TypeScript.
(List of Programming Languages): Include lang-typescript.texi.
* gettext-tools/doc/xgettext.texi: Document the -L TypeScript and -L TSX
options.
* gettext-tools/src/x-typescript-impl.h: New file.
* gettext-tools/src/x-typescript.h: New file.
* gettext-tools/src/x-typescript.c: New file.
* gettext-tools/src/x-typescriptx.h: New file.
* gettext-tools/src/x-typescriptx.c: New file.
* gettext-tools/src/xgettext.c: Include x-typescript.h, x-typescriptx.h.
(flag_table_typescript, flag_table_typescriptx): New variables.
(main): Invoke init_flag_table_typescript, init_flag_table_typescriptx,
x_typescript_extract_all, x_typescriptx_extract_all, x_typescript_keyword,
x_typescriptx_keyword.
(usage): Document the -L TypeScript and -L TSX options.
(xgettext_record_flag): Support format_javascript with TypeScript and TSX.
(language_to_extractor, extension_to_language): Support TypeScript and TSX.
* gettext-tools/src/FILES: Mention x-typescript.h, x-typescript.c,
x-typescriptx.h, x-typescriptx.c, x-typescript-impl.h.
* gettext-tools/src/Makefile.am (noinst_LIBRARIES): Reference LIBXGETTEXTTS.
(noinst_HEADERS): Add x-typescript.h, x-typescriptx.h, x-typescript-impl.h.
(LIBXGETTEXTTS): Add libxgettextts3.a, libxgettextts4.a.
(libxgettextts3_a_SOURCES, libxgettextts3_a_CPPFLAGS): New variables.
(libxgettextts4_a_SOURCES, libxgettextts4_a_CPPFLAGS): New variables.
(xgettext_SOURCES): Add x-typescript.c, x-typescriptx.c.
* gettext-tools/tests/xgettext-javascript-6: Improve comments.
* gettext-tools/tests/xgettext-typescript-1: New file, based on
gettext-tools/tests/xgettext-javascript-1.
* gettext-tools/tests/xgettext-typescript-2: New file, based on
gettext-tools/tests/xgettext-javascript-2.
* gettext-tools/tests/xgettext-typescript-3: New file, based on
gettext-tools/tests/xgettext-javascript-3.
* gettext-tools/tests/xgettext-typescript-4: New file, based on
gettext-tools/tests/xgettext-javascript-4.
* gettext-tools/tests/xgettext-typescript-5: New file, based on
gettext-tools/tests/xgettext-javascript-5.
* gettext-tools/tests/xgettext-typescript-6: New file, based on
gettext-tools/tests/xgettext-javascript-6.
* gettext-tools/tests/xgettext-typescript-7: New file, based on
gettext-tools/tests/xgettext-javascript-7.
* gettext-tools/tests/Makefile.am (TESTS): Add the new tests.
* NEWS: Mention the TypeScript support.